Phosphor and light-emitting equipment using phosphor

ABSTRACT

An object of the present invention is to provide an inorganic phosphor having fluorescence properties emitting an orange or red light which has a longer wavelength as compared with the cases of conventional sialon phosphors activated with a rare earth. 
     The invention relates to a design of white light-emitting diode rich in a red component and having good color-rendering properties by employing a solid solution crystal phase phosphor which uses as a host crystal an inorganic compound having the same crystal structure as that of a CaSiAlN 3  crystal phase and to which M (wherein M is one or two or more elements selected from the group consisting of Mn, Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, and Yb) is added as an emission center.

FIELD OF THE INVENTION

The present invention relates to a phosphor mainly composed of an inorganic compound and applications thereof. More specifically, the applications relate to light-emitting equipments such as a lighting equipment and an image display unit as well as a pigment and an ultraviolet absorbent, which utilize a property possessed by the phosphor, i.e., a characteristic of emitting fluorescence having a long wavelength of 570 nm or longer.

BACKGROUND ART

Phosphors are used for a vacuum fluorescent display (VFD), afield emission display (FED), a plasma display panel (PDP), a cathode ray tube (CRT), a white light-emitting diode (LED), and the like. In all these applications, it is necessary to provide energy for exciting the phosphors in order to cause emission from the phosphors. The phosphors are excited by an excitation source having a high energy, such as a vacuum ultraviolet ray, an ultraviolet ray, an electron beam, or a blue light to emit a visible light. However, as a result of exposure of the phosphors to the above excitation source, there arises a problem of decrease of luminance of the phosphors and hence a phosphor exhibiting no decrease of luminance has been desired. Therefore, a sialon phosphor has been proposed as a phosphor exhibiting little decrease of luminance instead of conventional silicate phosphors, phosphate phosphors, aluminate phosphors, sulfide phosphors, and the like.

The sialon phosphor is produced by the production process outlined below. First, silicon nitride (Si₃N₄), aluminum nitride (AlN), calcium carbonate (CaCO₃), and europium oxide (Eu₂O₃) are mixed in a predetermined molar ratio and the mixture is held at 1700° C. for 1 hour in nitrogen at 1 atm (0.1 MPa) and is baked by a hot pressing process to produce the phosphor (e.g., cf. Patent Literature 1). The α-sialon activated with Eu obtained by the process is reported to be a phosphor which is excited by a blue light of 450 to 500 nm to emit a yellow light of 550 to 600 nm. However, in the applications of a white LED and a plasma display using an ultraviolet LED as an excitation source, phosphors emitting lights exhibiting not only yellow color but also orange color and red color have been desired. Moreover, in a white LED using a blue LED as an excitation source, phosphors emitting lights exhibiting orange color and red color have been desired in order to improve color-rendering properties.

As a phosphor emitting a light of red color, an inorganic substance (Ba_(2-x)Eu_(x)Si₅N₈: x=0.14 to 1.16) obtained by activating a Ba₂Si₅N₈ crystal phase with Eu has been reported in an academic literature (cf. Non-Patent Literature 1) prior to the present application. Furthermore, in Chapter 2 of a publication “On new rare-earth doped M-Si—Al—O—N materials” (cf. Non-Patent Literature 2), a phosphor using a ternary nitride of an alkali metal and silicon having various compositions, M_(x)Si_(y)N_(z) (M=Ca, Sr, Ba, Zn; x, y, and z represent various values) as a host has been reported. Similarly, M_(x)Si_(y)N_(z):Eu (M=Ca, Sr, Ba, Zn; z=2/3x+4/3y) has been reported in U.S. Pat. No. 6,582,663 (Patent Literature 2).

As other sialon, nitride or oxynitride phosphors, there are known in JP-A-2003-206431 (Patent Literature 3) phosphors using MSi₃N₅, M₂Si₄N₇, M₄Si₆N₁₁, M₉Si₁₁N₂₃, M₁₆Si₁₅O₆N₃₂, M₁₃ Si₁₈Al₁₂O₁₈N₃₆, MSi₅Al₂ON₉, and M₃Si₅AlON₁₀ (wherein M represents Ba, Ca, Sr or a rare earth element) as host crystals, which are activated with Eu or Ce. Among them, phosphors emitting a light of red color have been also reported. Moreover, LED lighting units using these phosphors are known. Furthermore, JP-A-2002-322474 (Patent Literature 4) has reported a phosphor wherein an Sr₂Si₅N₈ or SrSi₇N₁₀ crystal phase is activated with Ce.

In JP-A-2003-321675 (Patent Literature 5), there is a description of LxMyN_((2/3x+4/3y)):Z (L is a divalent element such as Ca, Sr, or Ba, M is a tetravalent element such as Si or Ge, and Z is an activator such as Eu) phosphor and it describes that addition of a minute amount of Al exhibits an effect of suppressing afterglow. Moreover, a slightly reddish warm color white emitting apparatus is known, wherein the phosphor and a blue LED are combined. Furthermore, JP-A-2003-277746 (Patent Literature 6) reports phosphors constituted by various combinations of L Element, M Element, and Z Element as L×MyN_((2/3x+4/3y)):Z phosphors. JP-A-2004-10786 (Patent Literature 7) describes a wide range of combinations regarding an L-M-N:Eu,Z system but there is not shown an effect of improving emission properties in the cases that a specific composition or crystal phase is used as a host.

The representative phosphors in Patent Literatures 2 to 7 mentioned above contain nitrides of a divalent element and a tetravalent element as host crystals and phosphors using various different crystal phases as host crystals have been reported. The phosphors emitting a light of red color are also known but the emitting luminance of red color is not sufficient by excitation with a blue visible light. Moreover, they are chemically unstable in some compositions and thus their durability is problematic.

[Non-Patent Literature 1]

-   H. A. Hoppe, and other four persons, “Journal of Physics and     Chemistry of Solids” 2000, vol. 61, pages 2001-2006     [Non-Patent Literature 2] -   “On new rare-earth doped M-Si—Al—O—N materials” written by J. W. H.     van Krevel, TU Eindhoven 2000, ISBN, 90-386-2711-4     [Patent Literature 1] -   JP-A-2002-363554     [Patent Literature 2] -   U.S. Pat. No. 6,682,663     [Patent Literature 3] -   JP-A-2003-206481     [Patent Literature 4] -   JP-A-2002-322474     [Patent Literature 5] -   JP-A-2003-321675     [Patent Literature 6] -   JP-A-2003-277746     [Patent Literature 7] -   JP-A-2004-10786

As conventional art of lighting apparatus, a white light-emitting diode wherein a blue light-emitting diode element and a blue light-absorbing yellow light-emitting phosphor are combined is known and has been practically used in various lighting applications. Representative examples thereof include “a light-emitting diode” of Japanese Patent No. 2900928 (Patent Literature 8), “a light-emitting diode” of Japanese Patent No. 2927279 (Patent Literature 9), “a wavelength-converting molding material and a process for producing the same, and a light-emitting element” of Japanese Patent No. 3364229 (Patent Literature 10), and the like. Phosphors most frequently used in these light-emitting diode are yttrium.aluminum.garnet-based phosphors activated with cerium represented by the general formula: (Y,Gd)₃(Al,Ga):Ce³⁺.

However, there is a problem that the white light-emitting diode comprising a blue light-emitting diode element and the yttrium.aluminum.garnet-based phosphor has a characteristic of emitting a bluish-white light because of an insufficient red component and hence deflection is found in color-rendering properties.

Based on such a background, there has been investigated a white light-emitting diode wherein a red component which is short in the yttrium.aluminum.garnet-based phosphor is supplemented with another red phosphor by mixing and dispersing two kinds of phosphors. As such light-emitting diodes, “a white light-emitting diode” of JP-A-10-163535 (Patent Literature 11), “a nitride phosphor and a process for producing the same” of JP-A-2003-321675 (Patent Literature 5), and the like can be exemplified. However, a problem to be improved regarding color-rendering properties still remains also in these inventions, and hence it is desired to develop a light-emitting diode where the problem is solved. The red phosphor described in JP-A-10-163535 (Patent Literature 11) contains cadmium and thus there is a problem of environmental pollution. Although red light emitting phosphors including Ca_(1.97)Si₅N₈:Eu_(0.03) described in JP-A-2003-321675 (Patent Literature 5) as a representative example do not contain cadmium but further improvement of their emission intensities has been desired since luminance of the phosphor is low.

[Patent Literature 8]

-   Japanese Patent No. 2900928     [Patent Literature 9] -   Japanese Patent No. 2927279     [Patent Literature 10] -   Japanese Patent No. 3364229     [Patent Literature 11] -   JP-A-10-163535

DISCLOSURE OF THE INVENTION

The invention intends to reply such demands and an object thereof is to provide an inorganic phosphor which emits an orange or red light having a longer wavelength than that of conventional sialon phosphors activated with a rare earth, has a high luminance, and is chemically stable. Furthermore, another object of the invention is to provide alighting equipment excellent in color-rendering properties, an image display unit excellent in durability, a pigment, and an ultraviolet absorbent using such a phosphor.

Under such circumstances, the present inventors have conducted precise studies on phosphors using as a host an inorganic multi-element nitride crystal phase containing trivalent E Element such as Al in addition to divalent A Element such as Ca and tetravalent D Element such as Si as main metal elements and have found that a phosphor using an inorganic crystal phase having a specific composition or a specific crystal structure as a host emits an orange or red light having a longer wavelength than that of conventional sialon phosphors activated with a rare earth and also exhibits a higher luminance than that of the red phosphors hitherto reported containing a nitride or oxynitride as a host crystal.

Namely, as a result of extensive studies on inorganic compounds mainly composed of nitrides or oxynitrides containing M Element which becomes a light-emitting ion (wherein M Element is one or two or more elements selected from Mn, Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, and Yb) and divalent A Element (wherein A Element is one or two or more elements selected from Mg, Ca, Sr, and Ba), tetravalent D Element (wherein D Element is one or two or more elements selected from Si, Ge, Sn, Ti, Zr, and Hf), trivalent E Element (wherein E Element is one or two or more elements selected from B, Al, Ga, In, Sc, Y, La, Gd and Lu), and X Element (wherein X Element is one or two or more elements selected from O, N, and F), they have found that those having a specific composition region range and a specific crystal phase form phosphors emitting an orange light having a wavelength of 570 nm or longer or a red light having a wavelength of 600 nm or longer.

Furthermore, they have found that, among the above compositions, a solid solution crystal phase containing an inorganic compound having the same crystal structure as that of the CaAlSiN₃ crystal phase as a host crystal and incorporated with an optically active element M, particularly Eu as an emission center forms a phosphor emitting an orange or red light having an especially high luminance. Furthermore, they have found that a white light-emitting diode which has a high emission efficiency, is rich in a red component, and exhibits good color-rendering properties can be obtained by using the phosphor.

The host crystal of the phosphor of the invention achieves red-light emission exhibiting an unprecedented luminance by using the multi-element nitride wherein a trivalent element including Al as a representative is used as a main constitutive metal element, quite unlike the ternary nitrides containing divalent and tetravalent elements hitherto reported including L_(x)M_(y)N_((2/3x+4/3y)) as a representative. Moreover, the invention is a novel phosphor using a crystal phase having a composition and crystal structure quite different from the sialons such as M₁₃Si₁₈Al₁₂O₁₈N₃₆, MSi₅Al₂ON₉, and M₃Si₅AlON₁₀ (wherein M represents Ca, Ba, Sr, or the like) hitherto reported in Patent Literature 3 and the like and Ca_(1.47)Eu_(0.03)Si₉Al₃N₁₆ described in Chapter 11 of Non-Patent Literature 2 as a host. Furthermore, unlike the crystal phase containing Al in an amount of about: several hundreds of ppm described in Patent Literature 5, it is a phosphor using as a host a crystal phase wherein a trivalent element including Al as a representative is a main constitutive element of the host crystal.

In general, a phosphor wherein an inorganic host crystal is activated with Mn or a rare earth metal as an emission center element M changes an emitting color and luminance depending on an electron state around M Element. For example, in a phosphor containing divalent Eu as the emission center, light emission of blue color, green color, yellow color, or red color has been reported by changing the host crystal. Namely, even in the case that the composition is resemble, when the crystal structure of the host or the atom position in the crystal structure to which M is incorporated is changed, the emitting color and luminance become quite different and thus the resulting phosphor is regarded as a different one. In the invention, a multi-element nitride containing divalent-trivalent-tetravalent elements different from conventional ternary nitrides containing divalent and tetravalent elements is used as a host crystal and furthermore, a crystal phase having a crystal structure quite different from that of the sialon composition hitherto reported is used as a host. Thus, the phosphor having such a crystal phase as a host has not hitherto been reported. In addition, the phosphor containing the composition and crystal structure of the invention as a host exhibits a red light emission having luminance higher than that of those containing a conventional crystal structure as a host.

The above CaAlSiN₃ crystal phase itself is a nitride whose formation in the process of baking an Si₃N₄—AlN—CaO based raw material is confirmed by ZHEN-KUN-HUANG et al. for the purpose of aiming at a heat-resistant material. A process of the formation and a mechanism of the formation are precisely reported in an academic literature (c.f. Non-Patent Literature 3), which has been published prior to the present application.

[Non-Patent Literature 3]

-   ZHEN-KUN-HUANG and other two persons, “Journal of Materials Science     Letters” 1985, vol. 4, pages 255-259

As mentioned above, the CaAlSiN₃ crystal phase itself is confirmed in the progress of the study of sialons. Also, from the circumstances, the content: of the report described in the above literature only mentions heat-resistant properties and the literature does not describe any matter that an optically active element may be dissolved in the crystal phase and the dissolved crystal phase may be used as a phosphor. Moreover, over the period from that time to the present invention, there is no investigation to use it as a phosphor. Namely, the important findings that a substance obtained by dissolving an optically active element in CaAlSiN₃ crystal phase is a novel substance and it is usable as a phosphor capable of being excited with an ultraviolet ray and a visible light and exhibiting an orange or red light emission having a high luminance have been first found by the present inventors. As a result of further extensive studies based on the findings, the inventors have succeeded in providing a phosphor showing an emission phenomenon with a high luminance in a specific wavelength region by the constitutions described in the following (1) to (24). Moreover, they have also succeeded in providing a lighting equipment and an image display unit having excellent characteristics by the constitutions described in the following (25) to (37) by using the phosphor. Furthermore, by applying the inorganic compound as the phosphor to the constitutions described in the following (38) to (39), they have also succeeded in providing a pigment and an ultraviolet absorbent. Namely, as a result of a series of experiments and studies based on the above findings, the invention has succeeded in providing a phosphor emitting a light with a high luminance in a long wavelength region as well as a lighting equipment, an image display unit, a pigment, and an ultraviolet absorbent utilizing the phosphor. The constitutions are as described in the following (1) to (39).

(1) A phosphor comprising an inorganic compound which is a composition containing at least M Element, A Element, D Element, E Element, and X Element (wherein M Element is one or two or more elements selected from the group consisting of Mn, Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, and Yb, A Element is one or two or more elements selected from the group consisting of divalent metal elements other than M Element, D Element is one or two or more elements selected from the group consisting of tetravalent metal elements, E Element is one or two or more elements selected from the group consisting of trivalent metal elements, and X Element is one or two or more elements selected from the group consisting of O, N, and F).

(2) The phosphor according to the above item (1), wherein the inorganic compound has the same crystal structure as that of CaAlSiN₃.

(3) The phosphor according to the above item (1) or (2), wherein the inorganic compound is represented by the composition formula M_(a)A_(b)D_(c)E_(d)X_(e) (wherein a+b=1 and M Element is one or two or more elements selected from the group consisting of Mn, Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, and Yb, A Element is one or two or more elements selected from the group consisting of divalent metal elements other than M Element, D Element is one or two or more elements selected from the group consisting of tetravalent metal elements, E Element is one or two or more elements selected from the group consisting of trivalent metal elements, and X Element is one or two or more elements selected from the group consisting of O, N, and F), wherein the parameters a, c, d, and e satisfy all the requirements: 0.00001≦a≦0.1  (i), 0.5≦c≦4  (ii), 0.5≦d≦8  (iii), 0.8×(2/3+4/3×c+d)≦e  (iv), and e≦1.2×(2/3+4/3×c+d)  (v).

(4) The phosphor according to the above item (3), wherein the parameters c and d satisfy the requirements of 0.5≦c≦1.8 and 0.5≦d≦1.8.

(5) The phosphor according to the above item (3) or (4), wherein the parameters c, d, and e are c=d=1 and e=3.

(6) The phosphor according to any one of the above items (1) to (5), wherein A Element is one or two or more elements selected from the group consisting of Mg, Ca, Sr, and Ba, D Element is one or two or more elements selected from the group consisting of Si, Ge, Sn, Ti, Zr, and Hf, and E Element is one or two or more elements selected from the group consisting of B, Al, Ga, In, Sc, Y, La, Gd, and Lu.

(7) The phosphor according to any one of the above items (1) to (6), which contains, at least, Eu in M Element, Ca in A Element, Si in D Element, Al in E Element, and N in X Element.

(8) The phosphor according to any one of the above items (1) to (7), wherein the inorganic compound is a CaAlSiN₃ crystal phase or a solid solution of a CaAlSiN₃ crystal phase.

(9) The phosphor according to any one of the above items (1) to (8), wherein M Element is Eu, A Element is Ca, D Element is Si, E Element is Al, and X Element is N or a mixture of N and O.

(10) The phosphor according to any one of the above items (1) to (9), which contains, at least, Sr in A Element.

(11) The phosphor according to the above item (10), wherein numbers of atoms of Ca and Sr contained in the inorganic compound satisfy 0.02 (number of atoms of Ca)/{(number of atoms of Ca)+(number of atoms of Sr)}<1.

(12) The phosphor according to any one of the above items (1) to (11), which contains, at least, N and O in X.

(13) The phosphor according to the above item (12), wherein numbers of atoms of O and N contained in the inorganic compound satisfy 0.5≦(number of atoms of N)/{(number of atoms of N)+(number of atoms of O)}≦1.

(14) The phosphor according to the above item (12) or (13), wherein the inorganic compound is represented by M_(a)A_(b)D_(1−x)E_(1+x)N_(3-x)O_(x) (wherein a+b=1 and 0<x≦0.5).

(15) The phosphor according to any one of the above items (1) to (14), wherein the inorganic compound is a powder having an average particle size of 0.1 μm to 20 μm and the powder is single crystal particles or an aggregate of single crystals.

(16) The phosphor according to any one of the above items (1) to (15), wherein total of impurity elements of Fe, Co, and Ni contained in the inorganic compound is 500 ppm or less.

(17) A phosphor which is constituted by a mixture of the phosphor comprising the inorganic compound according to anyone of the above items (1) to (16) and other crystal phase or an amorphous phase and wherein the content of the phosphor comprising the inorganic compound according to any one of the above items (1) to (16) is 20% by weight or more.

(18) The phosphor according to the above item (17), wherein the other crystal phase or amorphous phase is an inorganic substance having electroconductivity.

(19) The phosphor according to the above item (18), wherein the inorganic substance having electroconductivity is an oxide, oxynitride, or nitride containing one or two or more elements selected from the group consisting of Zn, Al, Ga, In, and Sn, or a mixture thereof.

(20) The phosphor according to the above item (17), wherein the other crystal phase or amorphous phase is an inorganic phosphor different from the phosphor according to any one of the above items (1) to (16).

(21) The phosphor according to any one of the above items (1) to (20), which emits a fluorescent light having a peak in the range of a wavelength of 570 nm to 700 nm by irradiation with an excitation source.

(22) The phosphor according to the above item (21), wherein the excitation source is an ultraviolet ray or a visible light having a wavelength of 100 nm to 600 nm.

(23) The phosphor according to the above item (21), wherein the inorganic compound is a CaAlSiN₃ crystal phase and Eu is dissolved in the crystal phase, and which emits a fluorescent light having a wavelength of 600 nm to 700 nm when irradiated with a light of 100 nm to 600 nm.

(24) The phosphor according to the above item (21), wherein the excitation source is an electron beam or an X-ray.

(25) The phosphor according to any one of the above items (21) to (24), wherein a color emitted at the irradiation with an excitation source satisfies a requirement: 0.45×0.7

as a value of (x, y) on the CIE chromaticity coordinates.

(26) A lighting equipment constituted by a light-emitting source and a phosphor, wherein at least the phosphor according to any one of the above items (1) to (25) is used.

(27) The lighting equipment according to the above item (26), wherein the light-emitting source is an LED emitting a light having a wavelength of 330 nm to 500 nm.

(28) The lighting equipment according to the above item (26) or (27), wherein the light-emitting source is an LED emitting a light having a wavelength of 330 nm to 420 nm and which emits a white light with mixing red, green, and blue lights by using the phosphor according to anyone of the above items (1) to (25), a blue phosphor having an emission peak at a wavelength of 420 nm to 500 nm with an excitation light of 330 nm to 420 nm, and a green phosphor having an emission peak at a wavelength of 500 nm to 570 nm with an excitation light of 330 nm to 420 nm.

(29) The lighting equipment according to the above item (26) or (27), wherein the light-emitting source is an LED emitting a light having a wavelength of 420 nm to 500 nm and which emits a white light by using the phosphor according to any one of the above items (1) to (25) and a green phosphor having an emission peak at a wavelength of 500 nm to 570 nm with an excitation light of 420 nm to 500 nm.

(30) The lighting equipment according to the above item (26) or (27), wherein the emitting source is an LED emitting a light having a wavelength of 420 nm to 500 nm and which emits a white light by using a phosphor according to any one of the above items (1) to (25) and a yellow phosphor having an emission peak at a wavelength of 550 nm to 600 nm with an excitation light of 420 nm to 500 nm.

(31) The lighting equipment according to the above item (30), wherein the yellow phosphor is a Ca-αsialon in which Eu is dissolved.

(32) An image display unit constituted by an excitation source and a phosphor, wherein at least the phosphor according to any one of the above items (1) to (25) is used.

(33) The image display unit according to the above item (32), wherein the excitation source is an LED emitting a light having a wavelength of 330 nm to 500 nm.

(34) The image display unit according to the above item (32) or (33), wherein the excitation source is an LED emitting a light having a wavelength of 330 nm to 420 nm and which emits a white light with mixing red, green, and blue lights by using the phosphor according to any one of the above items (1) to (25), a blue phosphor having an emission peak at a wavelength of 420 nm to 500 nm with an excitation light of 330 nm to 420 nm, and a green phosphor having an emission peak at a wavelength of 500 nm to 570 nm with an excitation light of 330 nm to 420 nm.

(35) The image display unit according to the above item (32) or (33), wherein the emitting source is an LED emitting a light having a wavelength of 420 nm to 500 nm and which emits a white light by using the phosphor according to any one of the above items (1) to (25) and a green phosphor having an emission peak at a wavelength of 500 nm to 570 nm with an excitation light of 420 nm to 500 nm.

(36) The image display unit according to the above item (32) or (33), wherein the emitting source is an LED emitting a light having a wavelength of 420 nm to 500 nm and which emits a white light by using the phosphor according to any one of the above items (1) to (25) and a yellow phosphor having an emission peak at a wavelength of 550 nm to 600 nm with an excitation light of 420 nm to 500 nm.

(37) The image display unit according to the above item (36), wherein the yellow phosphor is a Ca-αsialon in which Eu is dissolved.

(38) The image display unit according to the above items (32) to (37), wherein the image display unit is any of a vacuum fluorescent display (VFD), a field emission display (FED), a plasma display panel (PDP), and a cathode-ray tube (CRT).

(39) A pigment comprising the inorganic compound according to any one of the above items (1) to (25).

(40) An ultraviolet absorbent comprising the inorganic compound according to any one of the above items (1) to (25).

The phosphor of the invention contains a multi-element nitride containing a divalent element, a trivalent element, and a tetravalent element, particularly a crystal phase represented by CaAlSiN₃, another crystal phase having the same crystal structure as it, or a solid solution of these crystal phases as a main component and thereby exhibits light emission at a longer wavelength than that in the cases of conventional sialon and oxynitride phosphors, so that the phosphor of the invention is excellent as an orange or red phosphor. Even when exposed to an excitation source, the phosphor does not exhibit decrease of luminance and thus provides a useful phosphor which is suitably employed in VFD, FED, PDP, CRT, white LED, and the like. Moreover, among the phosphors, since the host of a specific inorganic compound has a red color and the compound absorbs an ultraviolet ray, it is suitable as a red pigment and an ultraviolet absorbent.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-1 is an X-ray diffraction chart of CaAlSiN₃.

FIGS. 1-2 is an X-ray diffraction chart of CaAlSiN₃ activated with Eu (Example 1).

FIG. 2 is a drawing illustrating a crystal structure model of CaAlSiN₃.

FIG. 3 is a drawing illustrating a crystal structure model of Si₂N₂O having a similar structure to the CaAlSiN₃ crystal phase.

FIG. 4 is a drawing illustrating emission spectra of phosphors (Examples 1 to 7).

FIG. 5 is a drawing illustrating excitation spectra of phosphors (Examples 1 to 7).

FIG. 6 is a drawing illustrating emission spectra of phosphors (Examples 8 to 11).

FIG. 7 is a drawing illustrating excitation spectra of phosphors (Examples 8 to 11).

FIG. 8 is a drawing illustrating emission spectra of phosphors (Examples 12 to 15).

FIG. 9 is a drawing illustrating excitation spectra of phosphors (Examples 12 to 15).

FIG. 10 is a drawing illustrating emission spectra of phosphors (Examples 16 to 25).

FIG. 11 is a drawing illustrating excitation spectra of phosphors (Examples 16 to 25).

FIG. 12 is a drawing illustrating emission spectra of phosphors (Examples 26 to 30).

FIG. 13 is a drawing illustrating excitation spectra of phosphors (Examples 26 to 30).

FIG. 14 is a schematic drawing of the lighting equipment (LED lighting equipment) according to the invention.

FIG. 15 is a schematic drawing of the image display unit (plasma display panel) according to the invention.

In this connection, with regard to the symbols in the figures, 1 represents a mixture of a red phosphor of the invention and a yellow phosphor or a mixture of a red phosphor of the invention, a blue phosphor, and a green phosphor, 2 represents an LED chip, 3 and 4 represent electroconductive terminals, 5 represents a wire bond, 6 represents a resin layer, 7 represents a container, 8 represents a red phosphor of the invention, 9 represents a green phosphor, 10 represents a blue phosphor, 11, 12, and 13 represent ultraviolet ray-emitting cells, 14, 15, 16, and 17 represent electrodes, 18 and 19 represent dielectric layers, 20 represents a protective layer, and 21 and 22 represent glass substrates.

BEST MODE FOR CARRYING OUT THE INVENTION

The following will describe the present invention in detail with reference to Examples of the invention.

The phosphor of the invention comprises an inorganic compound which is (1) a composition containing at least M Element, A Element, D Element, E Element, and X Element (wherein M Element is one or two or more elements selected from the group consisting of Mn, Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, and Yb, A Element is one or two or more elements selected from the group consisting of divalent metal elements other than M Element, D Element is one or two or more elements selected from the group consisting of tetravalent metal elements, E Element is one or two or more elements selected from the group consisting of trivalent metal elements, and X Element is one or two or more elements selected from the group consisting of O, N, and F) and is (2) (a) a crystal phase represented by the chemical formula CaAlSiN₃, (b) another crystal phase having the same crystal structure as that of the crystal phase, or (c) a solid solution of these crystal phases (hereinafter, these crystal phases are collectively referred to as “a CaAlSiN₃ family crystal phase”). Such a phosphor of the invention shows a particularly high luminance.

M Element is one or two or more elements selected from the group consisting of Mn, Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, and Yb. M Element is preferably one or two or more elements selected from the group consisting of Mn, Ce, Sm, Eu, Tb, Dy, Er, and Yb. M Element more preferably contains Eu and is still more preferably Eu.

A Element is one or two or more elements selected from the group consisting of divalent metal elements other than M Element. Particularly, A Element is preferably one or two or more elements selected from the group consisting of Mg, Ca, Sr, and Ba and is more preferably Ca.

D Element is one or two or more elements selected from the group consisting of tetravalent metal elements. Particularly, D Element is preferably one or two or more elements selected from the group consisting of Si, Ge, Sn, Ti, Zr, and Hf and is more preferably Si.

E Element is one or two or more elements selected from the group consisting of trivalent metal elements. Particularly, E Element is one or two or more elements selected from the group consisting of B, Al, Ga, In, Sc, Y, La, Gd, and Lu and is more preferably Al.

X Element is one or two or more elements selected from the group consisting of O, N, and F. Particularly, X Element is preferably composed of N or N and O.

The composition is represented by the composition formula M_(a)A_(b)D_(c)E_(d)X_(e). A composition formula is a ratio of numbers of the atoms constituting the substance and one obtained by multiplying a, b, c, d, and e by an arbitrary number has also the same composition. Therefore, in the invention, the following requirements are determined to the one obtained by recalculation for a, b, c, d, and e so as to be a+b=1.

In the invention, the values of a, c, d, and e are selected from the values satisfying all the following requirements: 0.00001≦a≦0.1  (i), 0.5≦c≦4  (ii), 0.5≦d≦8  (iii), 0.8×(2/3+4/3×c+d)≦e  (iv), e≦1.2×(2/3+4/3×c+d)  (v).

a represents an adding amount of M Element which becomes an emission center and the ratio a of numbers of atoms M and (M+A) (wherein a=M/(M+A)) in a phosphor is suitably from 0.00001 to 0.1. When a Value is less than 0.00001, the number of M becoming an emmision center is small and hence emission luminance decreases. When a Value is larger than 0.1, concentration quenching occurs owing to interference between M ions, so that luminance decreases.

In particular, in the case that M is Eu, a Value is preferably from 0.002 to 0.03 owing to high emission luminance.

c Value is the content of D Element such as Si and is an amount represented by 0.5≦c≦4. The value is preferably 0.5≦c≦1.8, more preferably c=1. When c Value is less than 0.5 and when the value is larger than 4, emission luminance decreases. In the range of 0.5≦c≦1.8, emission luminance is high and particularly, emission luminance is especially high at c=1. The reason therefor is that the ratio of formation of the CaAlSiN₃ family crystal phase to be described below increases.

d Value is the content of E Element such as Al and is an amount represented by 0.5≦d≦8 The value is preferably 0.5≦d≦1.8, more preferably d=1. When d Value is less than 0.5 and when the value is larger than 8, emission luminance decreases. In the range of 0.5≦d≦1.8, emission luminance is high and particularly, emission luminance is especially high at d=1. The reason therefor is that the ratio of formation of the CaAlSiN₃ family crystal phase to be described below increases.

e Value is the content of X Element such as N and is an amount represented by from 0.8×(2/3+4/3×c+d) to 1.2×(2/3+4/3×c+d). More preferably, e=3. The reason therefor is that the ratio of formation of the CaAlSiN₃ family crystal phase to be described below increases. When e Value is out of the range, emission luminance decreases.

Among the above compositions, compositions exhibiting a high emission luminance are those which contain, at least, Eu in M Element, Ca in A Element, Si in D Element, Al in E Element, and N in X Element. In particular, the composition are those wherein M Element is Eu, A Element is Ca, D Element is Si, E Element is Al, and X Element is N or a mixture of N and O.

The above CaAlSiN₃ crystal phase is an orthorhombic system and is a substance characterized by a crystal phase having lattice constants of a=9.8007(4) Å, b=5.6497(2) Å, and c=5.0627(2) Å and having indices of crystal plane described in the chart of FIGS. 1-1 and Table 4 in X-ray diffraction.

According to the crystal structure analysis of the CaAlSiN₃ crystal phase conducted by the inventors, the present crystal phase belongs to Cmc2₁ (36th space group of International Tables for Crystallography) and occupies an atomic coordinate position shown in Table 5. In this connection, the space group is determined by convergent beam electron diffraction and the atomic coordinate is determined by Rietveld analysis of X-ray diffraction results.

The crystal phase has a structure shown in FIG. 2 and has a similar skeleton to the Si₂N₂O crystal phase (mineral name: sinoite) shown in FIG. 3. Namely, the crystal phase is a crystal phase wherein the position of Si in the Si₂N₂O crystal phase is occupied by Si and Al and the positions of N and O are occupied by N, and Ca is incorporated as an interstitial element into a space of the skeleton formed by Si—N—O, and has a structure where the atomic coordinates are changed to the positions shown in Table 5 with the replacement of the elements. Si and Al occupy the Si position in the Si₂N₂O crystal phase in an irregularly distributed (disordered) state. Thus, this structure is named as a sinoite-type sialon structure.

The inorganic compound having the same crystal structure as CaAlSiN₃ shown in the invention means the inorganic compound which is a CaAlSiN₃ family crystal phase mentioned above. The inorganic compound having the same crystal structure as CaAlSiN₃ includes those having lattice constants changed by the replacement of the constitutive element(s) with other element(s) in addition to the substances showing the same diffraction as the results of X-ray diffraction of CaAlSiN₃. For example, a CaAlSiN₃ crystal phase, a solid solution of the CaAlSiN₃ crystal phase, and the like may be mentioned. Herein, one wherein the constitutive element (s) are replaced with other element (s) means a crystal phase wherein, in the case of the CaAlSiN₃ crystal phase, for example, Ca in the crystal phase is replaced with M Element (wherein M Element is one or two or more elements selected from the group consisting of Mn, Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, and Yb) and/or M Element and one or two or more elements selected from the group consisting of divalent metal elements other than Ca, preferably the group consisting of Mg, Sr, and Ba, Si is replaced with one or two or more elements selected from the group consisting of tetravalent metal elements other than Si, preferably the group consisting of Ge, Sn, Ti, Zr, and Hf, Al is replaced with one or two or more elements selected from the group consisting of trivalent metal elements other than Al, preferably the group consisting of B, Ga, In, Sc, Y, La, Gd, and Lu, and N is replaced with one or two or more elements selected from the group consisting of O and F. In this connection, the CaAlSiN₃ family crystal phase of the invention can be identified by X-ray diffraction or neutron-ray diffraction.

The CaAlSiN₃ family crystal phase is changed in lattice constants by the replacement of Ca, Si, Al, or N as the constitutive components with other element(s) or the dissolution of a metal element such as Eu but the atomic position determined by the crystal structure, the site occupied by the atom, and its coordinate is changed to not so large extent that the chemical bond between skeletal atoms is cleaved. In the invention, in the case that the lengths of chemical bonds of Al—N and Si—N (distance between adjacent atoms) calculated from the lattice constants and atomic coordinates determined by Rietveld analysis of the results of X-ray diffraction and neutron-ray diffraction with the space group of Cmc2₁ are within ±15% as compared with the length of the chemical bond calculated from the lattice constants and atomic coordinates of CaAlSiN₃ shown in Table 5, it is defined that the crystal phase has the same crystal structure. In this manner, a crystal phase is judged whether it is a CaAlSiN₃ family crystal phase or not. This judging standard is based on the fact that, when the length of the chemical bond changes beyond ±15%, the chemical bond is cleaved and another crystal phase is formed.

Furthermore, when the dissolved amount is small, the following method may be a convenient judging method of a CaAlSiN₃ family crystal phase. When the lattice constants calculated from the results of X-ray diffraction measured on a new substance and the peak position (20) of diffraction calculated using the indices of crystal plane in Table 4 are coincident with regard to main peaks, the crystal structures can be identified to be the same. As the main peaks, it is appropriate to conduct the judgment on about ten peaks exhibiting strong diffraction intensity. In that sense, Table 4 is a standard for identifying the CaAlSiN₃ family crystal phase and thus is of importance. Moreover, with regard to the crystal structure of the CaAlSiN₃ crystal phase, an approximate structure can be defined also using another crystal system such as a monoclinic system or a hexagonal system. In that case, the expression may be one using different space group, lattice constants, and indices of crystal plane but the results of X-ray diffraction are not changed and the identification method and identification results using the same are identical thereto. Therefore, in the invention, X-ray diffraction is analyzed as an orthorhombic system. The identification method of substances based on Table 4 will be specifically described in Example 1 to be described below and only a schematic explanation is conducted here.

A phosphor is obtained by activating a CaAlSiN₃ family crystal phase with M Element (wherein M Element is one or two or more elements selected from the group consisting of Mn, Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, and Yb). The phosphor having a particularly high luminance among the CaAlSiN₃ family crystal phases is a phosphor containing as a host a CaAlSiN₃ crystal phase using a combination that A is Ca, D is Si, E is Al, and X is N.

A phosphor using Ca_(x)Sr_(1-x)AlSiN₃ (wherein 0.02≦x≦1) crystal phase which is a crystal phase obtained by replacing part of Ca with Sr or its solid solution as host crystals, i.e., a phosphor wherein numbers of atoms of Ca and Sr contained in the inorganic compound satisfy 0.02≦(number of atoms of Ca)/{(number of atoms of Ca)+(number of atoms of Sr)}<1, becomes a phosphor exhibiting a shorter wavelength than that of the phosphor using as a host a CaAlSiN₃ crystal phase having a composition of the range.

The phosphor using as a host an inorganic compound containing nitrogen and oxygen is excellent in durability in a high-temperature air. In this case, durability at a high temperature is particularly excellent at the composition where numbers of atoms of O and N contained in the inorganic compound satisfy 0.5≦(number of atoms of N)/{(number of atoms of N)+(number of atoms of O)}1.

In the case that the inorganic compound containing nitrogen and oxygen is used as a host, since the ratio of formation of the CaAlSiN₃ family crystal phase increases at the composition represented by M_(a)A₁,D_(1−x)E_(1+x)N_(3−x)O_(x) (wherein a+b=1 and 0<x≦0.5), emission luminance is high. This is because trivalent N is replaced with divalent O by the number of the atom the same as the number of the tetravalent D Element replaced with trivalent E Element in the composition and hence charge neutrality is maintained, so that a stable CaAlSiN₃ family crystal phase is formed.

In the case that the phosphor comprising the inorganic compound having the same crystal structure as CaAlSiN₃ of the invention is used as a powder, the average particle size of the inorganic compound is preferably from 0.1 μm to 20 μm in view of dispersibility into the resin and fluidity of the powder. Moreover, the powder is single crystal particles or an aggregate of single crystals but emission luminance is further improved by using single crystal particles having an average particle size of 0.1 μM to 20 μm.

In order to obtain a phosphor exhibiting a high emission luminance, the amount of impurities contained in the inorganic compound is preferably as small as possible. In particular, since the contamination of a large amount of Fe, Co, and Ni impurity elements inhibits light emission, it is suitable that raw powders are selected and the synthetic steps are controlled so that the total of these elements becomes not more than 500 ppm.

In the invention, from the viewpoint of fluorescence emission, it is desirable that the nitride contain the CaAlSiN₃ family crystal phase as a constitutive component of the nitride in high purity and as much as possible, and is possibly composed of a single phase, but it may be composed of a mixture thereof with the other crystal phases or an amorphous phase within the range where the characteristics do not decrease. In this case, it is desirable that the content of the CaAlSiN₃ family crystal phase is 50% by weight or more in order to obtain a high luminance. Further preferably, when the content is 20% by weight or more, luminance is remarkably improved. In the invention, the range as a main component is a content of the CaAlSiN₃ family crystal phase of at least 20% by weight or more. The ratio of content of the CaAlSiN₃ family crystal phase can be determined from the ratio of the intensity of the strongest peaks in respective phases of the CaAlSiN₃ family crystal phase and the other crystal phases through the measurement of X-ray diffraction.

In the case that the phosphor of the invention is used for applications excited with an electron beam, electroconductivity can be imparted to the phosphor by mixing it with an inorganic substance having electroconductivity. As the inorganic substance having electroconductivity, there may be mentioned oxides, oxynitrides, or nitrides containing one or two or more elements selected from the group consisting of Zn, Al, Ga, In, and Sn, or mixtures thereof.

The phosphor of the invention can emit a red light by the combination of a specific host crystal and an activating element but, in the case that mixing with the other colors such as yellow color, green color, and blue color is necessary, it is possible to mix inorganic phosphors emitting lights of these colors according to necessity.

The phosphors of the invention exhibit different excitation spectra and fluorescent spectra depending on the composition and hence can be set at those having various emission spectra by suitably selecting and combining them. The embodiment maybe appropriately set at a required spectrum based on the application. Particularly, one wherein Eu is added to the CaAlSiN₃ crystal phase in a composition of 0.0001≦(number of atoms of Eu)/{(number of atoms of Eu)+(number of atoms of Ca)}≦0.1 exhibits emission of a light having a peak in the range of a wavelength of 600 nm to 700 nm when excited with a light having a wavelength in the range of 100 nm to 600 nm, preferably 200 nm to 600 nm, and exhibits excellent emission characteristics as red fluorescence.

The phosphors of the invention obtained as above are characterized in that they have a wide excitation range of from an electron beam or an X-ray and an ultraviolet ray to a visible light, i.e., ultraviolet rays or visible lights having wavelengths from 100 nm to 600 nm, emit an orange to red light of 570 nm or longer, and particularly exhibit red color of 600 nm to 700 nm at a specific composition, and they exhibit a red light ranging 0.45≦x≦0.7 in terms of the value of (x, y) on CIE chromaticity coordinates, as compared with conventional oxide phosphors and existing sialon phosphors. Owing to the above emission characteristics, they are suitable for a lighting equipment, an image display unit, a pigment, and an ultraviolet absorbent. In addition, since they are not degraded even when exposed to a high temperature, they are excellent in heat resistance and also excellent in long-term stability under an oxidizing atmosphere and under a moist environment.

The phosphors of the invention do not limit the production process but a phosphor exhibiting a high luminance can be produced by the following process.

A high-luminance phosphor is obtained by baking a raw material mixture, which is a mixture of metal compounds and may constitute a composition represented by M, A, D, E, and X by baking the mixture, at a temperature range of 1200° C. to 2200° C. in an inert atmosphere containing nitrogen.

In the case of synthesizing CaAlSiN₃ activated with Eu, it is suitable to use a powder mixture of europium nitride or europium oxide, calcium nitride, silicon nitride, and aluminum nitride as a starting material.

Moreover, in the case of synthesizing a composition containing strontium, incorporation of strontium nitride in addition to the above affords a stable (Ca, Sr)AlSiN₃ crystal phase wherein part of the calcium atoms in the crystal phase is replaced with strontium, whereby a high-luminance phosphor is obtained.

In the case of synthesizing a phosphor using as a host CaAlSi(O, N)₃ and activated with Eu, wherein part of the nitrogen atom in the crystal phase is replaced with oxygen, a starting material of a mixture of europium nitride, calcium nitride, silicon nitride, and aluminum nitride is preferable in the composition of a small oxygen content since the material has a high reactivity and the synthesis in high yields is possible. In this case, as oxygen, oxygen impurity contained in the raw material powders of europium nitride, calcium nitride, silicon nitride, and aluminum nitride is used.

In the case of synthesizing a phosphor of a large oxygen content using CaAlSi(O, N)₃ activated with Eu as a host, when a mixture of either of europium nitride or europium oxide or a mixture thereof, anyone of calcium nitride, calcium oxide, or calcium carbonate or a mixture thereof, silicon nitride, and aluminum nitride or a mixture of aluminum nitride and aluminum oxide is used as a starting material, the material has a high reactivity and the synthesis in high yields is possible.

It is appropriate that the above mixed powder of the metal compounds is baked in a state that a volume filling rate is maintained to 40% or less. In this connection, the volume filling rate can be determined according to (bulk density of mixed powder)/(theoretical density of mixed powder)×100[%]. As a vessel, a boron nitride sintered article is suitable because of low reactivity with the metal compounds.

The reason why the powder is baked in a state that a volume filling rate is maintained to 40% or less is that baking in the state that a free space is present around the starting powder enables synthesis of a crystal phase having little surface defect since the CaAlSiN₃ family crystal phase as a reaction product grows in a free space and hence the contact of the crystal phases themselves decreases.

Next, a phosphor is synthesized by baking the resulting mixture of the metal compounds in a temperature range of 1200° C. to 2200° C. in an inert atmosphere containing nitrogen. Since the baking is conducted at a high temperature and the baking atmosphere is an inert atmosphere containing nitrogen, the furnace for use in the baking is a metal-resistor resistive heating type one or a graphite resistive heating type one and an electric furnace using carbon as a material for a high-temperature part of the furnace is suitable. As the method of the baking, a sintering method of applying no mechanical pressure externally, such as an atmospheric sintering method or a gas pressure sintering method is preferred since baking is conducted while the volume filling rate is maintained at 40% or less.

In the case that the powder aggregate obtained by the baking is strongly adhered, it is pulverized by means of a pulverizing machine usually used industrially, such as a ball mill or a jet mill and the like. The pulverization is conducted until the average particle size reaches 20 μm or less. Particularly preferred is an average particle size of 0.1 μm to 5 μm. When the average particle size exceeds 20 μm, fluidity of the powder and dispersibility thereof into resins become worse and emission intensity becomes uneven from part to part at the time when an emission apparatus is formed in combination with a light-emitting element. When the size becomes 0.1 μm or less, the amount of defects on the surface of a phosphor powder becomes large and hence emission intensity decreases in some phosphor compositions.

Of the phosphors of the invention, the phosphors using the inorganic compound containing nitrogen and oxygen as a host can be also produced by the following process.

It is a process wherein oxygen is allowed to exist in the raw material to be baked so that the ratio (percentage) of mol number of oxygen to total mol number of nitrogen and oxygen in the raw material to be baked (hereinafter referred to as an “oxygen existing ratio in a raw material”) becomes from 1% to 20% in a state of a bulk density of 0.05 g/cm³ to 1 g/cm³ at a baking temperature of 1200° C. to 1750° C. at the time when a starting mixed powder containing an elementary substance and/or compound of M Element, a nitride of A Element, a nitride of D Element, and a nitride of E Element is baked.

The oxygen existing ratio in a raw material means a ratio (percentage) of mol number of oxygen to total mol number of nitrogen and oxygen in the raw material to be baked at baking and the nitrogen in the raw material to be baked is nitrogen derived from the raw powder, while the oxygen includes oxygen to be incorporated from the baking atmosphere into the material to be baked at baking in addition to the oxygen contained in the raw powder beforehand. The oxygen existing ratio in a raw material can be determined by the measurement using an oxygen nitrogen analyzer. The oxygen existing ratio in a raw material is preferably from 2% to 15%.

The method of allowing oxygen to exist in such an oxygen existing ratio in a raw material at baking includes:

(1) a method of using raw nitrides containing a desired concentration of oxygen as raw materials to be baked,

(2) a method of allowing raw nitrides to contain a desired concentration of oxygen by heating the raw nitrides beforehand under an oxygen-containing atmosphere,

(3) a method of mixing a raw nitride powder with an oxygen-containing compound powder to form a raw material to be baked,

(4) a method of introducing oxygen into the raw material to be baked by contaminating oxygen in the baking atmosphere at baking of raw nitrides and oxidizing the raw nitrides at baking, and the like. In order to produce a high-luminance phosphor industrially stably, preferred is (1) the method of using raw nitrides containing a desired concentration of oxygen as raw materials to be baked or (3) the method of mixing a raw nitride powder with an oxygen-containing compound powder to form a raw material to be baked. In particular, more preferred is a method of using raw nitrides containing a desired concentration of oxygen as raw materials to be baked and also mixing the raw nitride powder with an oxygen-containing compound powder to form a raw material to be used, which is a combination of the above methods (1) and (3).

In this case, the oxygen-containing compound powder is selected from substances which form metal oxides at baking. As these substances, use can be made of oxides, inorganic acid salts such as nitrates, sulfates, and carbonates of respective metals, i.e., metals constituting the raw nitrides, organic acid salts such as oxalates and acetates thereof, oxygen-containing organometallic compounds, and the like, of respective metals, i.e., metals constituting the raw nitrides. However, from the viewpoints that oxygen concentration is easily controlled and association of impurity gases into the baking atmosphere can be suppressed at a low level, it is preferred to use metal oxides.

The oxygen existing ratio in raw material can be easily determined by conducting chemical analysis of all the raw materials. In particular, the ratio of nitrogen to oxygen can be determined by analyzing concentrations of nitrogen and oxygen.

The elementary substance and/or compound of M Element to be used as a raw material may be any substance as far as M Element is incorporated into a host crystal of the phosphor at a high temperature, including metals (elementary substances), oxides, nitrides, sulfides, halides, hydrides of M Element and also inorganic acid salts such as nitrates, sulfates, and carbonates, organic acid salts such as oxalates and acetates, organometallic compounds, and the like, and there is no limitation in its kind. However, from the viewpoint of good reactivity with other nitride materials, metals, oxides, nitrides, and halides of M Element are preferred and oxides are particularly preferred since the raw materials are available at a low cost and the temperature for phosphor synthesis can be lowered.

In the case of using at least Eu as M Element, use can be made of one or two or more of Eu metal containing Eu as a constitutive element, europium oxide such as EuO and Eu₂O₃, and various compounds such as EuN, EuH₃, Eu₂S₃, EuF₂, EuF₃, EuCl₂, EuCl₃, Eu (NO₃)₃, EU₂ (SO₄)₃, EU₂ (CO₃)₃, EU (C₂O₄)₃, EU (O-i-C₃H₇)₃, but Eu halides such as EuF₂, EuF₃, EuCl₂, and EuCl₃ are preferred since they have an effect of accelerating crystal growth. Moreover, Eu₂O₃ and Eu metal are also preferred since a phosphor having excellent characteristics can be synthesized from them. Of these, Eu₂O₃ is particularly preferred, which is cheap in a raw material cost, has little deliquescency, and enables synthesis of a high-luminance phosphor at a relatively low temperature.

As raw materials for elements other than M Element, i.e., raw materials for A, D, and E Elements, nitrides thereof are usually used. Examples of nitrides of A Element include one or two or more of Mg₃N₂, Ca₃N₂, Sr₃N₂, Ba₃N₂, Zn₃N₂, and the like, examples of nitrides of D Element include one or two or more of Si₃N₄, Ge₃N₄, Sn₃N₄, Ti₃N₄, Zr₃N₄, Hf₃N₄, and the like, and examples of nitrides of E Element include one or two or more of AlN, GaN, InN, ScN, and the like. The use of powders thereof is preferred since a phosphor having excellent emission characteristics can be produced.

In particular, the use, as raw materials of A Element, of a highly active and highly reactive nitride material having mol number of oxygen of 1% to 20% relative to the total mol number of nitrogen and oxygen remarkably accelerates the solid phase reaction between the raw mixed powder of nitrides and, as a result, it becomes possible to lower the baking temperature and atmosphere gas pressure at baking without subjecting the raw mixed powder to compression molding. For the same reason, it is preferred to use, as a raw material of A Element, a nitride material particularly having mol number of oxygen of 2% to 15% relative to the total mol number of nitrogen and oxygen.

When the bulk density of the raw mixed powder is too small, the solid phase reaction is difficult to proceed owing to small contact area between the powdery raw materials and hence an impurity phase which cannot lead to synthesis of a preferred phosphor may remain in a large amount. On the other hand, when the bulk density is too large, the resulting phosphor may become a hard sintered one, which not only requires a long-term pulverization step after baking but also tends to lower luminance of the phosphor. Therefore, the bulk density is preferably from 0.15 g/cm³ to 0.8 g/cm³.

When the baking temperature of the raw mixed powder is too low, the solid phase reaction is difficult to proceed and the aimed phosphor cannot be synthesized. On the other hand, when it is too high, not only unproductive baking energy is consumed but also evaporation of nitrogen from the starting material and the produced substance increases and hence there is a tendency that the aimed phosphor cannot be produced unless the pressure of nitrogen which constitutes part of atmosphere gas is increased to a very high pressure. Therefore, the baking temperature is preferably from 1300° C. to 1700° C. The baking atmosphere of the raw mixed powder is in principle an inert atmosphere or a reductive atmosphere but the use of an atmosphere containing a minute amount of oxygen wherein the oxygen concentration is in the range of 0.1 to 10 ppm is preferred since it becomes possible to synthesize a phosphor at a relatively low temperature.

Moreover, the pressure of atmosphere gas at baking is usually 20 atm (2 MPa) or lower. A high-temperature baking equipment comprising a strong heat-resistant vessel is required for a pressure exceeding 20 atm and hence the cost necessary for baking becomes high, so that the pressure of the atmosphere gas is preferably 10 atm (1 MPa) or lower. In order to prevent contamination of oxygen in the air, the pressure is preferably slight higher than 1 atm (0.1 MPa). In the case that air-tightness of the baking furnace is wrong, when the pressure is 1 atm (0.1 MPa) or lower, a lot of oxygen contaminates the atmosphere gas and hence it is difficult to obtain a phosphor having excellent characteristics.

Furthermore, the holding time at the maximum temperature at baking is usually from 1 minute to 100 hours. When the holding time is too short, the solid phase reaction between raw mixed powders does not sufficiently proceed and an aimed phosphor cannot be obtained. When the holding time is too long, not only unproductive baking energy is consumed but also nitrogen is eliminated from the surface of the phosphor and the fluorescence characteristics deteriorate. For the same reasons, the holding time is preferably from 10 minutes to 24 hours.

As explained in the above, the CaAlSiN₃ family crystal phase phosphor of the invention exhibits a higher luminance than that of conventional sialon phosphors and, since decrease in luminance of the phosphor is small when it is exposed to an excitation source, it is a phosphor suitable for VFD, FED, PDP, CRT, white LED, and the like.

The lighting equipment of the invention is constituted by the use of at least a light-emitting source and the phosphor of the invention. As the lighting equipment, there may be mentioned an LED lighting equipment, a fluorescent lamp, and the like. The LED lighting equipment can be produced by known methods as described in JP-A-5-152609, JP-A-7-99345, Japanese Patent No. 2927279, and so forth with the phosphor of the invention. In this case, the light-emitting source is desirably one emitting a light having a wavelength of 330 to 500 nm, and particularly preferred is an ultraviolet (or violet) LED light-emitting element of 330 to 420 nm or a blue LED light-emitting element of 420 to 500 nm.

As these light-emitting elements, there exist an element comprising a nitride semiconductor such as GaN or InGaN and the like and, by adjusting the composition, it may be employed as a light-emitting source which emits a light having a predetermined wavelength.

In the lighting equipment, in addition to the method of using the phosphor of the invention solely, by the combined use thereof with a phosphor having other emission characteristics, a lighting equipment emitting a desired color can be constituted. As one example, there is a combination of an ultraviolet LED light-emitting element of 330 to 420 nm with a blue phosphor excited at the wavelength and having an emission peak at a wavelength of 420 nm to 500 nm, a green phosphor excited at the wavelength of 330 to 420 nm and having an emission peak at a wavelength of 500 nm to 570 nm, and the phosphor of the invention. There may be mentioned BaMgAl₁₀O₁₇:Eu as the blue phosphor and BaMgAl₁₀O₁₇:Eu,Mn as the green phosphor. In this constitution, when the phosphors are irradiated with an ultraviolet ray emitted by the LED, red, green, and blue lights are emitted and a white lighting equipment is formed by mixing the lights.

As an alternative method, there is a combination of a blue LED light-emitting element of 420 to 500 nm with a yellow phosphor excited at the wavelength and having an emission peak at a wavelength of 550 nm to 600 nm and the phosphor of the invention. As such a yellow phosphor, there may be mentioned (Y, Gd)₂ (Al, Ga)₅O₁₂: Ce described in Japanese Patent No. 2927279 and α-sialon:Eu described in JP-A-2002-363554. Of these, a Ca-α-sialon in which Eu is dissolved is preferred owing to high emission luminance. In this constitution, when the phosphors are irradiated with a blue light emitted by the LED, two lights having red and yellow colors are emitted and the lights are mixed with the blue light of LED itself to form a lighting equipment exhibiting a white color or a reddish lamp color.

As another method, there is a combination of a blue LED light-emitting element of 420 to 500 nm with a green phosphor excited at the wavelength and having an emission peak at a wavelength of 500 nm to 570 nm and the phosphor of the invention. As such a green phosphor, there may be mentioned Y₂Al₅O₁₂:Ce. In this constitution, when the phosphors are irradiated with a blue light emitted by the LED, two lights having red and green colors are emitted and the lights are mixed with the blue light of LED itself to form a white lighting equipment.

The image display unit of the invention is constituted by at least an excitation source and the phosphor of the invention and includes a vacuum fluorescent display (VFD), a field emission display (FED), a plasma display panel (PDP), a cathode ray tube (CRT), and the like. The phosphor of the invention is confirmed to emit a light by excitation with a vacuum ultraviolet ray of 100 to 190 nm, an ultraviolet ray of 190 to 380 nm, an electron beam, or the like. Thus, by the combination of any of these excitation sources and the phosphor of the invention, the image display unit as above can be constituted.

Since the specific inorganic compound of the invention has a red object color, it can be used as a red pigment or a red fluorescent pigment. When the inorganic compound of the invention is irradiated with illumination of sunlight, fluorescent lamp, or the like, a red object color is observed and the compound is suitable as an inorganic pigment owing to good coloring and no deterioration over a long period of time. Therefore, there is an advantage that the coloring does not decrease over a long period of time when it is used in coatings, inks, colors, glazes, colorants added to plastic products or the like. The nitride of the invention absorbs ultraviolet rays and hence is suitable as an ultraviolet absorbent. Therefore, when the nitride is used as a coating or applied on the surface of plastic products or kneaded into the products, the effect of shielding ultraviolet rays is high and thus the effect of protecting the products from ultraviolet degradation is high.

EXAMPLES

The following will describe the invention further in detail with reference to the following Examples but they are disclosed only for the purpose of easy understanding of the invention and the invention is not limited to these Examples.

Example 1

As raw powders were used a silicon nitride powder having an average particle size of 0.5 μm, an oxygen content of 0.93% by weight, and an α-type content of 92%, an aluminum nitride powder having a specific surface area of 3.3 m²/g and an oxygen content of 0.79%, a calcium nitride powder, and europium nitride synthesized by nitriding metal europium in ammonia.

In order to obtain a compound represented by the composition formula: Eu_(0.008)Ca_(0.992)AlSiN₃ (Table 1 shows parameters for designed composition, Table 2 shows designed composition (% by weight), and Table 3 shows a mixing composition of a raw powder), the silicon nitride powder, the aluminum nitride powder, the calcium nitride powder, and the europium nitride powder were weighed so as to be 33.8578% by weight, 29.6814% by weight, 35.4993% by weight, and 0.96147% by weight, respectively, followed by 30 minutes of mixing by means of an agate mortar and pestle. Thereafter, the resulting mixture was allowed to fall freely into a crucible made of boron nitride through a sieve of 500 μm to fill the crucible with the powder. The volume-filling rate of the powder was about 25%. In this connection, respective steps of weighing, mixing, and molding of the powders were all conducted in a globe box capable of maintaining a nitrogen atmosphere having a moisture content of 1 ppm or less and an oxygen content of 1 ppm or less.

The mixed powder was placed in a crucible made of boron nitride and set in a graphite resistive heating-type electric furnace. The baking operations were conducted as follows: the baking atmosphere was first vacuumed by a diffusion pump, heated from room temperature to 800° C. at a rate of 500° C. per hour, and pressurized to 1 MPa by introducing nitrogen having a purity of 99.999% by volume at 800° C., and the temperature was elevated to 1800° C. at a rate of 500° C. per hour and held at 1800° C. for 2 hours.

After baking, the resulting baked product was roughly pulverized and then was pulverized by hand using a crucible and mortar made of silicon nitride sintered compact, followed by filtering through a sieve having a mesh of 30 μm. When the particle distribution was measured, the average particle size was found to be 15 μm.

The constitutive crystal phase of the resulting synthetic powder was identified according to the following procedure. First, in order to obtain pure CaAlSiN₃ containing no M Element as a standard substance, the silicon nitride powder, the aluminum nitride powder, and the calcium nitride powder were weighed so as to be 34.088% by weight, 29.883% by weight, and 36.029% by weight, respectively, followed by 30 minutes of mixing by means of an agate mortar and pestle in a globe box. Then, the mixture was placed in a crucible made of boron nitride and set in a graphite resistive heating-type electric furnace. The baking operations were conducted as follows: the baking atmosphere was first vacuumed by a diffusion pump, heated from warm room to 800° C. at a rate of 500° C. per hour, and pressurized to 1 MPa by introducing nitrogen having a purity of 99.999% by volume at 800° C., and the temperature was elevated to 1800° C. at a rate of 500° C. per hour and held at 1800° C. for 2 hours. The synthesized sample was pulverized by means of an agate mortar and then measurement of powder X-ray diffraction was conducted using Kα line of Cu. As a result, the resulting chart shows a pattern illustrated in FIGS. 1-1 and the compound was judged to be a CaAlSiN₃ crystal phase based on indexing shown in Table 4. The crystal phase is an orthorhombic system, which has lattice constants of a=9.8007(4) Å, b=5.6497(2) Å, and c=5.0627 (2) Å. A space group determined by convergent beam electron diffraction using TEM is Cmc2₁ (36th space group of International Tables for Crystallography). Furthermore, the atomic coordinate position of each element determined by the Rietveld analysis using the space group is as shown in Table 5. The measured intensity of X-ray diffraction and the calculated intensity computed by the Rietveld method from the atomic coordinates show a good coincidence as shown in Table 4.

Next, the synthesized compound represented by the composition formula: Eu_(0.008)Ca_(0.992)AlSiN₃ was pulverized by means of an agate mortar and then measurement of powder X-ray diffraction was conducted using Kα line of Cu. As a result, the resulting chart is shown in FIGS. 1-2 and the compound was judged to be a CaAlSiN₃ family crystal phase based on indexing shown in Table 4.

The composition analysis of the powder was conducted by the following method. First, 50 mg of the sample was placed in a platinum crucible and 0.5 g of sodium carbonate and 0.2 g of boric acid were added thereto, followed by heating and melting the whole. Thereafter, the melt was dissolved in 2 ml of hydrochloric acid to be a constant volume of 100 ml, whereby a solution for measurement: was prepared. By subjecting the liquid sample to ICP emission spectrometry, the amounts of Si, Al, Eu, and Ca in the powder sample were quantitatively determined. Moreover, 20 mg of the sample was charged into a Tin capsule, which was then placed in a nickel basket. Then, using TC-436 Model oxygen and nitrogen analyzer manufactured by LECO, oxygen and nitrogen in the powder sample were quantitatively determined. The results of the measurement were as follows: Eu: 0.86±0.01% by weight, Ca: 28.9±0.1% by weight, Si: 20.4±0.1% by weight, Al: 19.6±0.1% by weight, N, 28.3±0.2% by weight, O: 2.0±0.1% by weight. In comparison with the indicated % by weight in the designed composition shown in Table 2, an oxygen content is especially high. The reason therefor is attributed to impurity oxygen contained in silicon nitride, aluminum nitride, and calcium nitride, which were employed as raw materials. In this composition, the ratio of number of atoms of N and O, N/(0+N) corresponds to 0.942. The composition of the synthesized inorganic compound calculated from the analytical results of all the elements is EU_(0.0078)Ca_(0.9922)Si_(0.9997)Al_(0.9996)N_(2.782)O_(0.172). In the invention, one wherein part of N is replaced with 0 is also included in the scope of the invention and, even in that case, a high-luminance red phosphor is obtained.

As a result of irradiation of the powder with a lamp emitting a light having a wavelength of 365 nm, emission of a red light was confirmed. As a result of measurement of emission spectrum (FIG. 4) and excitation spectrum (FIG. 5) of the powder using a fluorescence spectrophotometer, with regard to the peak wavelengths of the excitation and emission spectra (Table 6), it was found that the peak of the excitation spectrum was present at 449 nm and it was a phosphor having a peak at a red light of 653 nm in the emission spectrum with excitation at 449 nm. The emission intensity of the peak was 10655 counts. In this connection, since the count value varies depending on the measuring apparatus and conditions, the unit is an arbitrary unit. Moreover, the CIE chromaticity determined from the emission spectrum with excitation at 449 nm was red color of x=0.6699 and y=0.3263.

TABLE 1 Parameters for designed composition M Element A Element D Element E Element X Element Eu Mg Ca Sr Ba Si Al N Example a Value b Value c Value d Value e Value 1 0.008 0 0.992 0 0 1 1 3 2 0.008 0 0 0 0.992 1 1 3 3 0.008 0 0.1984 0 0.7936 1 1 3 4 0.008 0 0.3968 0 0.5952 1 1 3 5 0.008 0 0.5952 0 0.3968 1 1 3 6 0.008 0 0.7936 0 0.1984 1 1 3 7 0.008 0 0.8928 0 0.0992 1 1 3 8 0.008 0 0.8928 0.0992 0 1 1 3 9 0.008 0 0.7936 0.1984 0 1 1 3 10 0.008 0 0.6944 0.2976 0 1 1 3 11 0.008 0 0.5952 0.3968 0 1 1 3 12 0.008 0 0.496 0.496 0 1 1 3 13 0.008 0 0.3968 0.5952 0 1 1 3 14 0.008 0 0.1984 0.7936 0 1 1 3 15 0.008 0 0 0.992 0 1 1 3 16 0.008 0.0992 0.8928 0 0 1 1 3 17 0.008 0.1984 0.7936 0 0 1 1 3 18 0.008 0.2976 0.6944 0 0 1 1 3 19 0.008 0.3968 0.5952 0 0 1 1 3 20 0.008 0.496 0.496 0 0 1 1 3 21 0.008 0.5952 0.3968 0 0 1 1 3 22 0.008 0.6944 0.2976 0 0 1 1 3 23 0.008 0.7936 0.1984 0 0 1 1 3 24 0.008 0.8928 0.0992 0 0 1 1 3 25 0.008 0.992 0 0 0 1 1 3

TABLE 2 Designed composition (% by weight) Example Eu Mg Ca Sr Ba Si Al N 1 0.88056 0 28.799 0 0 20.3393 19.544 30.4372 2 0.51833 0 0 0 58.0887 11.9724 11.5042 17.9163 3 0.56479 0 3.69436 0 50.6371 13.0457 12.5356 19.5225 4 0.62041 0 8.11634 0 41.7178 14.3304 13.77 21.4451 5 0.68818 0 13.5044 0 30.8499 15.8958 15.2742 23.7876 6 0.77257 0 20.2139 0 17.3165 17.8451 17.1473 26.7047 7 0.82304 0 24.2261 0 9.2238 19.0107 18.2673 28.449 8 0.85147 0 25.063 6.08788 0 19.6674 18.8984 29.4318 9 0.82425 0 21.5659 11.7864 0 19.0386 18.2941 28.4907 10 0.79871 0 18.2855 17.1319 0 18.4487 17.7273 27.608 11 0.7747 0 15.2022 22.156 0 17.8943 17.1945 26.7783 12 0.7521 0 12.2989 26.887 0 17.3722 16.6929 25.997 13 0.73078 0 9.56019 31.3497 0 16.8797 16.2196 25.26 14 0.69157 0 4.52361 39.5568 0 15.974 15.3494 23.9047 15 0.65635 0 0 46.928 0 15.1605 14.5677 22.6874 16 0.89065 1.76643 26.2163 0 0 20.5725 19.768 30.7862 17 0.90098 3.57383 23.5736 0 0 20.8111 19.9973 31.1432 18 0.91155 5.42365 20.869 0 0 21.0553 20.2319 31.5086 19 0.92238 7.3174 18.1001 0 0 21.3052 20.4722 31.8828 20 0.93346 9.25666 15.2646 0 0 21.5612 20.7181 32.2659 21 0.94481 11.2431 12.3602 0 0 21.8235 20.9701 32.6583 22 0.95645 13.2784 9.3843 0 0 22.0922 21.2283 33.0604 23 0.96837 15.3645 6.33418 0 0 22.3676 21.4929 33.4725 24 0.98059 17.5033 3.20707 0 0 22.6499 21.7642 33.895 25 0.99313 19.6967 0 0 0 22.9394 22.0425 34.3283

TABLE 3 Mixing composition (% by weight) Example EuN Mg3N2 Ca3N2 Sr3N2 Ba3N2 Si3N4 AlN 1 0.96147 0 35.4993 0 0 33.8578 29.6814 2 0.56601 0 0 0 62.0287 19.932 17.4733 3 0.61675 0 4.55431 0 54.0709 21.7185 19.0395 4 0.67747 0 10.0054 0 44.546 23.8569 20.9142 5 0.75146 0 16.6472 0 32.9406 26.4624 23.1982 6 0.84359 0 24.9176 0 18.4896 29.7068 26.0424 7 0.89868 0 29.863 0 9.84853 31.6467 27.7431 8 0.92972 0 30.8943 6.73497 0 32.7397 28.7012 9 0.9 0 26.5838 13.0394 0 31.6931 27.7837 10 0.87212 0 22.5403 18.9531 0 30.7114 26.9231 11 0.84592 0 18.7397 24.5116 0 29.7886 26.1142 12 0.82124 0 15.1609 29.7457 0 28.9197 25.3524 13 0.79797 0 11.785 34.6832 0 28.1 24.6339 14 0.75516 0 5.57638 43.7635 0 26.5926 23.3124 15 0.71671 0 0 51.9191 0 25.2387 22.1255 16 0.97249 2.44443 32.3156 0 0 34.2459 30.0216 17 0.98377 4.94555 29.058 0 0 34.6429 30.3697 18 0.99531 7.50535 25.724 0 0 35.0493 30.726 19 1.00712 10.1259 22.3109 0 0 35.4654 31.0907 20 1.01922 12.8095 18.8158 0 0 35.8914 31.4642 21 1.03161 15.5582 15.2356 0 0 36.3278 31.8467 22 1.04431 18.3747 11.5674 0 0 36.7749 32.2387 23 1.05732 21.2613 7.80768 0 0 37.2332 32.6404 24 1.07067 24.2208 3.9531 0 0 37.7031 33.0523 25 1.08435 27.256 0 0 0 38.1849 33.4748

TABLE 4 Observed Calculated intensity intensity Peak Indices 2θ Spacing arbitrary arbitrary No. h k l degree Å unit unit Results of X-ray diffraction (No. 1) 1 2 0 0 18.088 4.90033 1129 360 2 1 1 0 18.109 4.89464 3960 1242 3 2 0 0 18.133 4.90033 569 178 4 1 1 0 18.154 4.89464 1993 614 5 1 1 1 25.288 3.51896 3917 5137 6 1 1 1 25.352 3.51896 1962 2539 7 3 1 0 31.61 2.82811 72213 68028 8 0 2 0 31.648 2.82483 38700 36445 9 3 1 0 31.691 2.82811 35723 33624 10 0 2 0 31.729 2.82483 19158 18014 11 0 0 2 35.431 2.53137 75596 78817 12 0 0 2 35.522 2.53137 37579 39097 13 3 1 1 36.357 2.469 100000 101156 14 0 2 1 36.391 2.4668 56283 56923 15 3 1 1 36.451 2.469 49334 49816 16 0 2 1 36.484 2.4668 27873 28187 17 4 0 0 36.647 2.45017 15089 15187 18 2 2 0 36.691 2.44732 11430 11483 19 4 0 0 36.741 2.45017 7481 7507 20 2 2 0 36.785 2.44732 5661 5676 21 2 0 2 40.058 2.24902 5403 5599 22 1 1 2 40.068 2.24847 76 79 23 2 0 2 40.162 2.24902 2678 2767 24 1 1 2 40.172 2.24847 38 39 25 2 2 1 40.924 2.20339 14316 13616 26 2 2 1 41.031 2.20339 7123 6730 27 3 1 2 48.207 1.88616 21363 21434 28 0 2 2 48.233 1.88519 19002 19072 29 3 1 2 48.334 1.88616 10584 10591 30 0 2 2 48.361 1.88519 9407 9424 31 5 1 0 49.159 1.85184 2572 2513 32 4 2 0 49.185 1.85092 4906 4795 33 1 3 0 49.228 1.84939 253 239 34 5 1 0 49.289 1.85184 1346 1242 35 4 2 0 49.315 1.85092 2565 2369 36 1 3 0 49.359 1.84939 130 118 37 4 0 2 51.892 1.76054 6201 6580 38 2 2 2 51.926 1.75948 6187 6564 39 4 0 2 51.031 1.76054 3075 3251 40 2 2 2 52.064 1.75948 3078 3243 41 5 1 1 52.579 1.73915 2042 2153 42 4 2 1 52.604 1.73839 188 199 43 1 3 1 52.645 1.73712 282 298 44 5 1 1 52.72 1.73915 1002 1064 45 4 2 1 52.745 1.73839 92 98 46 1 3 1 52.786 1.73712 139 147 47 6 0 0 56.272 1.63344 17721 17283 48 3 3 0 56.344 1.63155 33576 32772 49 6 0 0 56.425 1.63344 8757 8541 50 3 3 0 56.496 1.63155 16569 16195 Results of X-ray diffraction (No. 2) 51 1 1 3 57.738 1.59541 771 461 52 1 1 3 57.895 1.59541 447 228 53 3 3 1 59.475 1.5529 987 445 54 3 3 1 59.638 1.5529 504 220 55 5 1 2 62.045 1.4946 421 460 56 4 2 2 62.068 1.49412 3824 4174 57 1 3 2 62.105 1.49331 518 571 58 5 1 2 62.217 1.4946 209 227 59 4 2 2 62.239 1.49412 1886 2063 60 1 3 2 62.276 1.49331 257 282 61 3 1 3 64.218 1.44918 25890 27958 62 0 2 3 64.239 1.44874 19133 20597 63 3 1 3 64.396 1.44918 12851 13816 64 0 2 3 64.418 1.44874 9441 10178 65 6 2 0 66.013 1.41406 6643 6534 66 0 4 0 66.099 1.41242 2793 2737 67 6 2 0 66.198 1.41406 3327 3229 68 0 4 0 66.284 1.41242 1385 1315 69 2 2 3 67.344 1.3893 3814 3509 70 2 2 3 67.534 1.3893 1869 1735 71 6 0 2 68.281 1.3725 18466 17968 72 3 3 2 68.345 1.37138 27397 26670 73 6 0 2 68.474 1.3725 9086 8881 74 3 3 2 68.538 1.37138 13419 13182 75 6 2 1 68.885 1.36193 22014 21698 76 0 4 1 68.97 1.36046 11088 10930 77 7 1 0 69.056 1.35899 827 815 78 6 2 1 69.081 1.36193 10883 10725 79 5 3 0 69.112 1.35802 573 564 80 2 4 0 69.161 1.35717 4360 4307 81 0 4 1 69.166 1.36046 5470 5403 82 7 1 0 69.252 1.35899 409 403 83 5 3 0 69.308 1.35802 283 279 84 2 4 0 69.358 1.35717 2165 2129 85 7 1 1 71.871 1.31252 263 170 86 5 3 1 71.926 1.31165 684 445 87 2 4 1 71.974 1.31088 810 520 88 7 1 1 72.077 1.31252 132 84 89 5 3 1 72.133 1.31165 345 220 90 2 4 1 72.181 1.31088 399 257 91 0 0 4 74.975 1.26568 3881 3841 92 0 0 4 75.194 1.26568 1960 1899 93 5 1 3 76.274 1.24734 1812 1659 94 4 2 3 76.294 1.23705 865 798 95 1 3 3 76.328 1.24659 516 478 96 5 1 3 76.497 1.24734 826 820 97 4 2 3 76.518 1.24705 403 395 98 1 3 3 76.552 1.24659 241 237 99 6 2 2 77.212 1.2345 6989 7316 100 0 4 2 77.293 1.23341 1114 1179 Results of X-ray diffraction (No. 3) 101 6 2 2 77.439 1.2345 3384 3619 102 0 4 2 77.521 1.23341 542 583 103 2 0 4 77.888 1.22547 2080 2260 104 1 1 4 77.895 1.22538 237 253 105 8 0 0 77.917 1.22508 32 35 106 4 4 0 78.025 1.22366 144 155 107 2 0 4 78.118 1.22547 1016 1118 108 1 1 4 78.125 1.22538 113 125 109 8 0 0 78.148 1.22508 16 17 110 4 4 0 78.256 1.22366 69 77 111 7 1 2 80.08 1.19735 671 762 112 5 3 2 80.134 1.19668 45 51 113 2 4 2 80.18 1.1961 2092 2383 114 7 1 2 80.32 1.19735 332 377 115 5 3 2 80.373 1.19668 22 25 116 2 4 2 80.42 1.1961 1032 1179 117 4 4 1 80.724 1.18941 1023 1169 118 4 4 1 80.966 1.18941 504 579 119 3 3 3 82.095 1.17299 566 560 120 3 3 3 82.343 1.17299 249 277 121 3 1 4 83.634 1.15527 2395 2418 122 0 2 4 83.654 1.15504 2611 2637 123 3 1 4 83.889 1.15527 1191 1197 124 0 2 4 83.909 1.15504 1309 1306 125 4 0 4 86.47 1.12451 531 492 126 2 2 4 86.496 1.12423 1172 1090 127 8 2 0 86.525 1.12394 278 258 128 7 3 0 86.558 1.12359 934 864 129 1 5 0 86.663 1.1225 737 688 130 4 0 4 86.738 1.12451 262 244 131 2 2 4 86.765 1.12423 585 540 132 8 2 0 86.793 1.12394 139 128 133 7 3 0 86.826 1.12359 467 428 134 1 5 0 86.932 1.1225 367 341 135 8 0 2 88.617 1.10273 102 99 136 4 4 2 88.722 1.10169 1094 1054 137 8 0 2 88.895 1.10273 50 49 138 4 4 2 89.001 1.10169 525 523 139 8 2 1 89.18 1.09723 495 480 140 7 3 1 89.213 1.09691 551 552 141 1 5 1 89.318 1.09588 123 123 142 8 2 1 89.461 1.09723 239 238 143 7 3 1 89.494 1.09691 271 274 144 1 5 1 89.6 1.09588 60 61 145 6 2 3 90.581 1.08386 8698 8736 146 0 4 3 90.66 1.08312 4187 4201 147 6 2 3 90.869 1.08386 4305 4332 148 0 4 3 90.949 1.08312 2067 2083 149 9 1 0 92.171 1.06928 921 787 150 6 4 0 92.269 1.06839 820 696 Results of X-ray diffraction (No. 4) 151 3 5 0 92.329 1.06786 846 709 152 9 1 0 92.467 1.06928 466 390 153 6 4 0 92.566 1.06839 403 346 154 3 5 0 92.626 1.06786 407 352 155 7 1 3 93.395 1.05845 882 812 156 5 3 3 93.448 1.058 1111 1042 157 2 4 3 93.494 1.05759 575 533 158 7 1 3 93.697 1.05845 439 403 159 5 3 3 93.75 1.058 557 517 160 2 4 3 93.797 1.05759 286 264 161 9 1 1 94.828 1.0462 8091 7983 162 6 4 1 94.928 1.04537 8273 8175 163 5 1 4 94.979 1.04494 392 387 164 3 5 1 94.987 1.04487 8587 8469 165 4 2 4 94.999 1.04477 1156 1143 166 1 3 4 95.032 1.0445 609 602 167 9 1 1 95.139 1.0462 4016 3962 168 6 4 1 92.238 1.04537 4108 4058 169 5 1 4 95.29 1.04494 195 192 170 3 5 1 95.298 1.04487 4269 4204 171 4 2 4 95.31 1.04477 575 567 172 1 3 4 95.344 1.0445 304 299 173 8 2 2 97.156 1.02724 533 515 174 7 3 2 97.189 1.02697 983 946 175 1 5 2 97.296 1.02613 878 840 176 8 2 2 97.479 1.02724 264 256 177 7 3 2 97.513 1.02697 482 470 178 1 5 2 97.62 1.02613 426 417 179 6 0 4 100.691 1.00049 5749 5826 180 3 3 4 100.751 1.00005 7565 7696 181 6 0 4 101.035 1.00049 2904 2897 182 3 3 4 101.096 1.00005 3864 3826 183 1 1 5 101.945 0.99155 99 95 184 4 4 3 102.075 0.99064 700 665 185 1 1 5 102.297 0.99155 50 47 186 4 4 3 102.428 0.99064 353 331 187 9 1 2 102.889 0.98501 2904 2773 188 6 4 2 102.99 0.98431 1613 1539 189 3 5 2 103.051 0.9839 2352 2255 190 9 1 2 103.247 0.98501 1414 1379 191 6 4 2 103.349 0.98431 774 766 192 3 5 2 103.41 0.9839 1122 1122 193 10 0 0 103.617 0.98007 899 903 194 5 5 0 103.786 0.97893 803 806 195 10 0 0 103.979 0.98007 451 449 196 5 5 0 104.15 0.97893 411 401 197 5 5 1 106.535 0.96113 323 378 198 5 5 1 106.917 0.96113 183 188 199 3 1 5 107.807 0.95329 6210 6468 200 0 2 5 107.827 0.95316 3757 3932 Results of X-ray diffraction (No. 5) 201 3 1 5 108.198 0.95329 3120 3223 202 0 2 5 108.219 0.95316 1888 1959 203 6 2 4 109.525 0.94308 3209 2974 204 9 3 0 109.591 0.9427 3570 3280 205 0 4 4 109.609 0.9426 656 602 206 0 6 0 109.779 0.94161 1454 1338 207 6 2 4 109.93 0.94308 1622 1483 208 9 3 0 109.995 0.9427 1792 1636 209 0 4 4 110.014 0.9426 329 300 210 0 6 0 110.185 0.94161 731 667 211 2 2 5 110.828 0.93563 247 223 212 8 2 3 110.859 0.93546 1336 1210 213 7 3 3 110.894 0.93526 103 93 214 1 5 3 111.007 0.93463 519 457 215 2 2 5 111.242 0.93563 119 111 216 8 2 3 111.273 0.93546 647 604 217 7 3 3 111.308 0.93526 49 46 218 1 5 3 111.422 0.93463 246 228 219 9 3 1 112.432 0.92677 457 453 220 7 1 4 112.538 0.9262 96 97 221 10 2 0 112.59 0.92592 528 532 222 5 3 4 112.595 0.9259 832 826 223 0 6 1 112.625 0.92574 381 385 224 2 4 4 112.645 0.92563 174 173 225 8 4 0 112.676 0.92546 1400 1394 226 2 6 0 112.819 0.92469 115 117 227 9 3 1 112.859 0.92677 222 226 228 7 1 4 112.966 0.9262 47 48 229 10 2 0 113.018 0.92592 261 265 230 5 3 4 113.023 0.9259 405 412 231 0 6 1 113.053 0.92574 188 192 232 2 4 4 113.074 0.92563 86 87 233 8 4 0 113.105 0.92546 688 696 234 2 6 0 113.249 0.92469 56 59 235 10 0 2 114.874 0.91396 1273 1144 236 5 5 2 115.055 0.91303 1086 961 237 10 0 2 115.321 0.91396 627 571 238 10 2 1 115.495 0.91081 149 143 239 5 5 2 115.504 0.91303 501 480 240 8 4 1 115.583 0.91038 71 69 241 2 6 1 115.729 0.90965 825 800 242 10 2 1 115.948 0.91081 76 71 243 8 4 1 116.036 0.91038 36 34 244 2 6 1 116.184 0.90965 418 400 245 9 1 3 117.036 0.90323 3785 3707 246 6 4 3 117.147 0.9027 6351 6249 247 3 5 3 117.214 0.90238 8809 8688 248 9 1 3 117.503 0.90323 1876 1854 249 6 4 3 117.615 0.9027 3153 3125 250 3 5 3 117.682 0.90238 4393 4345 Results of X-ray diffraction (No. 6) 251 5 1 5 120.23 0.88842 190 173 252 4 2 5 120.253 0.88831 1117 1030 253 1 3 5 120.291 0.88814 215 197 254 5 1 5 120.727 0.88842 92 87 255 4 2 5 120.751 0.88831 556 516 256 1 3 5 120.789 0.88814 107 99 257 9 3 2 121.365 0.88343 9276 8712 258 0 6 2 121.573 0.88253 3149 2999 259 9 3 2 121.874 0.88343 4581 4365 260 0 6 2 122.085 0.88253 1548 1503 261 8 0 4 122.102 0.88027 825 792 262 11 1 0 122.144 0.88009 48 46 263 4 4 4 122.227 0.87974 1161 1113 264 7 5 0 122.331 0.8793 55 53 265 4 6 0 122.416 0.87894 35 34 266 8 0 4 122.619 0.88027 411 397 267 11 1 0 122.661 0.88009 23 23 268 4 4 4 122.745 0.87974 570 558 269 7 5 0 122.85 0.8793 27 26 270 4 6 0 122.937 0.87894 17 17 271 10 2 2 124.703 0.86958 1189 1160 272 8 4 2 124.8 0.86919 1867 1838 273 2 6 2 124.96 0.86856 465 456 274 10 2 2 125.249 0.86958 604 582 275 11 1 1 125.334 0.86709 855 833 276 8 4 2 125.347 0.86919 947 923 277 2 6 2 125.509 0.86856 234 229 278 7 5 1 125.528 0.86633 30 29 279 4 6 1 125.617 0.86599 2025 1984 280 11 1 1 125.888 0.86709 430 418 281 7 5 1 126.084 0.86633 15 15 282 4 6 1 126.174 0.86599 1035 996 283 3 3 5 127.101 0.86033 236 232 284 3 3 5 127.677 0.86033 128 117

TABLE 5 Data of crystal structure of CaAlSiN3 CaAlSiN3 Space Group (#36) Cmc2₁ Lattice constants (Å) a b c 9.8007 (4) 5.6497 (2) 5.0627 (2) Site x y z Si/Al 8 (b) 0.1734 (2) 0.1565 (3) 0.0504 (4) N1 8 (b) 0.2108 (4) 0.1205 (8) 0.3975 (2) N2 4 (a) 0 0.2453 (7)  0.0000 (10) Ca 4 (a) 0 0.3144 (3) 0.5283 SiN2O Space Group (#36) Cmc2₁ Lattice constants (Å) a b c 8.8717 5.4909 4.8504 Site x y z Si/Al 8 (b) 0.1767 0.1511 0.0515 N 8 (b) 0.2191 0.1228 0.3967 O 4 (a) 0 0.2127 0

TABLE 6 Peak wavelength and intensity of excitation emission spectra Emission Emission Excitation Excitation intensity wavelength intensity wavelength Example arbitrary unit nm arbitrary unit nm 1 10655 653 10595 449 2 622 600 617 449 3 2358 655 2336 449 4 4492 655 4471 449 5 5985 655 5975 449 6 6525 654 6464 449 7 6796 654 6748 449 8 8457 654 8347 449 9 8384 650 8278 449 10 7591 650 7486 449 11 7368 645 7264 449 12 7924 641 7834 449 13 8019 637 7920 449 14 8174 629 8023 449 15 1554 679 1527 401 16 8843 657 8779 449 17 5644 658 5592 449 18 6189 658 6199 449 19 5332 657 5261 449 20 5152 661 5114 449 21 4204 663 4177 449 22 3719 667 3710 449 23 3800 664 3833 449 24 2090 679 2097 449 25 322 679 326 453

Comparative Example 1

Using the raw powders described in Example 1, in order to obtain pure CaAlSiN₃ containing no M Element, the silicon nitride powder, the aluminum nitride powder, and the calcium nitride powder were weighed so as to be 34.088% by weight, 29.883% by weight, and 36.029% by weight, respectively, and a powder was prepared in the same manner as in Example 1. According to the measurement of X-ray diffraction, it was confirmed that the synthesized powder was CaAlSiN₃. When excitation and emission spectra of the synthesized inorganic compound were measured, any remarkable emission peak was not observed in the range of 570 nm to 700 nm.

Examples 2 to 7

As Examples 2 to 7 were prepared inorganic compounds having a composition in which part or all of Ca was replaced with Ba.

The inorganic compounds were prepared in the same manner as in Example 1 with the exception of the compositions shown in Tables 1, 2, and 3. According to the measurement of X-ray diffraction, it was confirmed that the synthesized powders were inorganic compounds having the same crystal structure as that of CaAlSiN₃. When excitation and emission spectra of the synthesized inorganic compound were measured, as shown in FIGS. 4 and 5, and Table 6, it was confirmed that they were red phosphors having an emission peak in the range of 570 nm to 700 nm, which were excited with an ultraviolet ray or a visible light of 350 nm to 600 nm. Incidentally, since emission luminance decreases as an added amount of Ba increases, a composition in the region where the added amount of Ba is small is preferred.

Examples 8 to 15

As Examples 8 to 15 were prepared inorganic compounds having a composition in which part or all of Ca was replaced with Sr.

Phosphors were prepared in the same manner as in Example 1 with the exception of the compositions shown in Tables 1, 2, and 3. According to the measurement of X-ray diffraction, it was confirmed that the synthesized powders were inorganic compounds having the same crystal structure as that of CaAlSiN₃. When excitation and emission spectra of the synthesized inorganic compound. were measured, as shown in FIGS. 6 and 7 (Examples 8 to 11), FIGS. 8 and 9 (Examples 12 to 15), and Table 6, it was confirmed that they were red phosphors having an emission peak in the range of 570 nm to 700 nm, which were excited with an ultraviolet ray or a visible light of 350 nm to 600 nm. Incidentally, emission luminance decreases as an added amount of Sr increases, but the wavelength of the emission peak shifts to a shorter wavelength side as compared with the addition of Ca alone. Therefore, in the case that it is desired to obtain a phosphor having a peak wavelength in the range of 600 nm to 650 nm, it is effective to replace part of Ca with Sr.

Examples 16 to 25

As Examples 16 to 25 were prepared inorganic compounds having a composition in which part or all of Ca was replaced with Mg.

Phosphors were prepared in the same manner as in Example 1 with the exception of the compositions shown in Tables 1, 2, and 3. According to the measurement of X-ray diffraction, it was confirmed that the synthesized powders were inorganic compounds having the same crystal structure as that of CaAlSiN₃. When excitation and emission spectra of the synthesized inorganic compound were measured, as shown in FIGS. 10 and 11, and Table 6, it was confirmed that they were red phosphors having an emission peak in the range of 570 nm to 700 nm, which were excited with an ultraviolet ray or a visible light of 350 nm to 600 nm. Incidentally, since emission luminance decreases as an added amount of Mg increases, a composition in the region where the added amount of Mg is small is preferred.

Examples 26 to 30

As Examples 26 to 30 were prepared inorganic compounds having a composition in which part of N was replaced with 0. In this case, since valence number is different between N and O, simple replacement does not result in neutrality of the total charge. Thus, the composition: Ca₆Si_(6-x)Al_(6+x)O_(x)N_(18-x)(0<x≦3) was investigated, which is a composition in which Si—N is replaced with Al—O.

Phosphors were prepared in the same manner as in Example 1 with the exception of the compositions shown in Tables 7 and 8. According to the measurement of X-ray diffraction, it was confirmed that the synthesized powders were inorganic compounds having the same crystal structure as that of CaAlSiN₃. When excitation and emission spectra of the synthesized inorganic compound were measured, as shown in FIGS. 12 and 13, it was confirmed that they were red phosphors having an emission peak in the range of 570 nm to 700 nm, which were excited with an ultraviolet ray or a visible light of 350 nm to 600 nm. Incidentally, since emission luminance decreases as an added amount of oxygen increases, a composition in the region where the added amount of oxygen is small is preferred.

TABLE 7 Parameters for designed composition M Element A Element D Element E Element X Element Eu Ca Si Al O N Example a Value b Value c Value d Value e Value 26 0.008 0.992 0.916667 1.083333 0.083333 2.919333 27 0.008 0.992 0.833333 1.166667 0.166667 2.836 28 0.008 0.992 0.75 1.25 0.25 2.752667 29 0.008 0.992 0.666667 1.333333 0.333333 2.669333 30 0.008 0.992 0.5 1.5 0.5 2.502667

TABLE 8 Mixing composition (% by weight) Example Si3N4 AIN Al203 Ca3N2 EuN 26 31.02 30.489 2.05 35.48 0.961 27 28.184 31.297 4.097 35.461 0.96 28 25.352 32.103 6.143 35.442 0.96 29 22.523 32.908 8.186 35.423 0.959 30 16.874 34.517 12.266 35.385 0.958

Examples 31 to 37

Using the same raw powders as in Example 1, in order to obtain inorganic compounds (showing mixing compositions of the raw powders in Table 9 and composition parameters in Table 10), the silicon nitride powder, the aluminum nitride powder, the calcium nitride powder, and the europium nitride powder were weighed, followed by 30 minutes of mixing by means of an agate mortar and pestle. Thereafter, the resulting mixture was molded using a mold by applying a pressure of 20 MPa to form a molded article having a diameter of 12 mm and a thickness of 5 mm. In this connection, respective steps of weighing, mixing, and molding of the powders were all conducted in a globe box capable of maintaining a nitrogen atmosphere having a moisture content of 1 ppm or less and an oxygen content of 1 ppm or less.

The molded article was placed in a crucible made of boron nitride and set in a graphite resistive heating-type electric furnace. The baking operations were conducted as follows: the baking atmosphere was first vacuumed by a diffusion pump, heated from warm room to 800° C. at a rate of 500° C. per hour, and pressurized to 1 MPa by introducing nitrogen having a purity of 99.999% by volume at 800° C., and the temperature was elevated to 1800° C. at a rate of 500° C. per hour and held at 1800° C. for 2 hours.

After baking, as a result of identification of constitutive crystal phase of the resulting sintered compact, it was judged to be a CaAlSiN₃ family crystal phase. As a result of irradiation of the powder with a lamp emitting a light having a wavelength of 365 nm, it was confirmed that it emits a red light. When excitation spectrum and emission spectrum of the powder were measured using a fluorescence spectrophotometer, as shown in Table 11, it was confirmed that it was a red phosphor having an emission peak in the range of 570 nm to 700 nm, which was excited with an ultraviolet ray or a visible light of 350 nm to 600 nm. Incidentally, since the measurement in these Examples was conducted using an apparatus different from that used in other Examples, the count values can be compared only within the range of Examples 31 to 37.

TABLE 9 Mixing composition of raw powder (unit: % by weight) Si3N4 AlN Ca3N2 EuN Example 31 34.07348 29.870475 35.995571 0.060475 Example 32 34.059016 29.857795 35.962291 0.120898 Example 33 34.030124 29.832467 35.895818 0.241591 Example 34 33.518333 29.383806 34.718285 2.379577 Example 35 33.185606 29.092121 33.952744 3.769529 Example 36 32.434351 28.433534 32.224251 6.907864 Example 37 31.418284 27.542801 29.886478 11.152437

TABLE 10 Parameters for designed composition a(Eu) b(Ca) c(Si) d(Al) e(N) Example 31 0.0005 0.9995 1 1 3 Example 32 0.001 0.999 1 1 3 Example 33 0.002 0.998 1 1 3 Example 34 0.02 0.98 1 1 3 Example 35 0.032 0.968 1 1 3 Example 36 0.06 0.94 1 1 3 Example 37 0.1 0.9 1 1 3

TABLE 11 Peak wavelength and intensity of excitation and emission spectra on fluorescence measurement Excitation spectrum Emission spectrum Peak Intensity Peak Intensity wavelength arbitrary wavelength arbitrary nm unit nm unit Example 31 479.6 387.322 609.2 391.066 Example 32 472.8 374.967 609.2 375.33 Example 33 480 427.41 612.6 428.854 Example 34 538 412.605 626.8 411.394 Example 35 546.4 414.434 629.2 413.009 Example 36 549.8 181.127 638.8 180.981 Example 37 549.4 89.023 644.4 92.763

Examples 38 to 56 and 60 to 76

As Examples 38 to 56 and 60 to 76 were prepared inorganic compounds having compositions in which c, d, and e parameters in the Eu_(a)Ca_(b)Si_(c)Al_(d)N_(e) composition were changed.

Phosphors were prepared in the same manner as in Example 1 with the exception of the compositions shown in Tables 12 and 13. According to the measurement of X-ray diffraction, it was confirmed that; the synthesized powders were powders containing inorganic compounds having the same crystal structure as that of CaAlSiN₃. When excitation and emission spectra of the synthesized inorganic compound were measured, as shown in Table 14, it was confirmed that they were red phosphors having an emission peak in the range of 570 nm to 700 nm, which were excited with an ultraviolet ray or a visible light of 350 nm to 600 nm.

TABLE 12 Parameters for designed composition a Value b Value Example (Eu) (Ca) c Value (Si) d Value (Al) e Value (N) 38 0.002 0.998 1 1 3 39 0.004 0.996 1 1 3 40 0.008 0.992 1 1 3 41 0.01 0.99 1 1 3 42 0.06 0.94 1 1 3 43 0.2 0.8 1 1 3 44 0.0107 0.9893 1 2 3 45 0.0133 0.9867 1 3 3 46 0.016 0.984 1 4 3 47 0.0187 0.9813 1 5 3 48 0.0213 0.9787 1 6 3 49 0.0107 0.9893 2 1 3 50 0.0133 0.9867 2 2 3 51 0.016 0.984 2 3 3 52 0.0187 0.9813 2 4 3 53 0.0213 0.9787 2 5 3 54 0.024 0.976 2 6 3 55 0.0133 0.9867 3 1 3 56 0.016 0.984 4 1 3 60 0.016 0.984 3 2 3 61 0.019 0.981 3 3 3 62 0.013 2.987 1 1 3 63 0.013 1.987 2 1 3 64 0.016 2.984 2 1 3 65 0.016 1.984 3 1 3 66 0.019 2.981 3 1 3 67 0.013 1.987 1 2 3 68 0.016 2.984 1 2 3 69 0.019 2.981 2 2 3 70 0.019 1.981 3 2 3 71 0.021 2.979 3 2 3 72 0.016 1.984 1 3 3 73 0.019 2.981 1 3 3 74 0.019 1.981 2 3 3 75 0.021 2.979 2 3 3 76 0.021 1.979 3 3 3

TABLE 13 Mixing composition of raw powder (unit: % by weight) Example Si3N4 AlN Ca3N2 EuN 38 34.01 29.81 35.94 0.24 39 33.925 29.74 35.855 0.48 40 33.765 29.595 35.68 0.96 41 33.685 29.525 35.595 1.195 42 31.785 27.86 33.59 6.77 43 27.45 24.06 29.01 19.485 44 25.99 45.56 27.465 0.985 45 21.125 55.55 22.325 1 46 17.795 62.39 18.805 1.01 47 15.37 67.365 16.245 1.02 48 13.53 71.15 14.295 1.025 49 50.365 22.07 26.61 0.955 50 41.175 36.09 21.755 0.975 51 34.825 45.785 18.4 0.99 52 30.17 52.89 15.94 1 53 26.615 58.32 14.06 1.01 54 23.805 62.6 12.58 1.015 55 60.235 17.6 21.22 0.95 56 66.775 14.635 17.64 0.95 60 51.135 29.88 18.015 0.97 61 44.425 38.94 15.65 0.98 62 19.63 17.205 62.235 0.93 63 39.705 17.4 41.96 0.94 64 32.765 14.36 51.94 0.93 65 49.61 14.495 34.955 0.94 66 42.175 12.325 44.57 0.93 67 20.35 35.675 43.01 0.965 68 16.72 29.315 53.015 0.95 69 28.615 25.08 45.36 0.95 70 43.27 25.285 30.485 0.955 71 37.505 21.915 39.635 0.945 72 17.24 45.34 36.44 0.98 73 14.565 38.295 46.175 0.965 74 29.37 38.615 31.04 0.975 75 25.395 33.39 40.255 0.96 76 38.37 33.63 27.03 0.97

TABLE 14 Peak wavelength of excitation and emission spectra on fluorescence measurement Excitation spectrum Emission spectrum Peak Strength Peak Intensity wavelength arbitrary wavelength arbitrary Example nm unit nm unit 38 449 8461 653 8479 39 449 7782 650 7832 40 449 8470 654 8551 41 449 9725 658 9762 42 449 6171 679 6182 43 449 1279 697 1245 44 449 7616 650 7763 45 449 7796 653 7854 46 449 6635 653 6685 47 449 6106 654 6149 48 449 5857 654 5907 49 333 5168 636 5211 50 332 4271 641 4342 51 330 4004 642 4046 52 335 3903 645 3954 53 335 3638 648 3703 54 337 3776 649 3799 55 316 2314 601 2348 56 407 1782 587 1906 60 412 4304 616 4330 61 409 4080 607 4099 62 467 3130 649 3135 63 322 2461 648 2461 64 449 1961 643 1996 65 316 3003 620 3003 66 319 3714 660 3714 67 449 4534 650 4586 68 467 3072 647 3067 69 449 6422 650 6426 70 449 7785 649 7856 71 449 4195 650 4179 72 449 4102 650 4095 73 461 2696 649 2693 74 449 9023 654 9146 75 450 5117 650 5180 76 322 6538 649 6538

Examples 77 to 84

As Examples 77 to 84 were prepared inorganic compounds having compositions in which D, E, and X Elements in the EU_(a)Ca_(b)D_(c)E_(d)X_(e) composition were changed.

Phosphors were prepared in the same manner as in Example 1 with the exception of the compositions shown in Tables 15 and 16. According to the measurement of X-ray diffraction, it was confirmed that the synthesized powders were powders containing inorganic compounds having the same crystal structure as that of CaAlSiN₃. When excitation and emission spectra of the synthesized inorganic compound were measured, as shown in Table 17, it was confirmed that they were red phosphors having an emission peak in the range of 570 nm to 700 nm, which were excited with an ultraviolet ray or a visible light of 350 nm to 600 nm.

TABLE 15 Parameters for designed composition M A D E X Element Element Element Element Element Eu Ca Si Ge Ti Hf Zr Al Y Sc N O Example a Value b Value c Value d Value e Value 77 0.008 0.992 1 0.95 0.05 3 78 0.008 0.992 1 0.9 0.1 3 79 0.008 0.992 1 0.8 0.2 3 80 0.008 0.992 0.95 0.05 1 3 81 0.008 0.992 1 0.97 0.03 3 0.045 82 0.008 0.992 0.97 0.03 1 3 0.06 83 0.008 0.992 0.95 0.05 1 3 0.1 84 0.008 0.992 0.97 0.03 1 3

TABLE 16 Mixing composition of raw powder (unit: % by weight) M Element A Element D Element E Element Example EuN Ca3N2 Si3N4 Ge3N4 TiO2 HfO2 ZrN AIN YN Sc2O3 77 0.95 34.7 33.1 27.6 3.65 78 0.9 34 32.4 25.55 7.15 79 0.9 32.6 31.1 21.8 13.7 80 0.95 34.95 31.65 3.25 29.2 81 0.95 35.3 33.65 28.6 1.5 82 0.95 35.25 32.6 1.75 29.45 83 0.9 33.5 30.35 7.2 28 84 0.95 35 32.4 2.35 29.3

TABLE 17 Peak wavelength and intensity of excitation and emission spectra on fluorescence measurement Excitation spectrum Emission spectrum Peak Strength Peak Intensity wavelength arbitrary wavelength arbitrary Example nm unit nm unit 77 449 6223 653 6380 78 449 4449 653 4565 79 449 3828 650 3937 80 449 2022 645 2048 81 449 5143 647 5481 82 450 2478 648 2534 83 449 3246 646 3303 84 449 8021 649 8050

Examples 85 to 92

As Examples 85 to 92 were prepared inorganic compounds having compositions in which M Element in the M_(a)Ca_(b)Si_(c)Al_(d) (N, O)_(e) composition were changed.

Phosphors were prepared in the same manner as in Example 1 with the exception of the compositions shown in Tables 18 and 19. According to the measurement of X-ray diffraction, it was confirmed that the synthesized powders were powders containing inorganic compounds having the same crystal structure as that of CaAlSiN₃. When excitation and emission spectra of the synthesized inorganic compound were measured, as shown in Table 20, is was confirmed that they were red phosphors having an emission peak in the range of 570 nm to 700 nm other than the phosphor of Example 89, which were excited with an ultraviolet ray or a visible light of 350 nm to 600 nm. In Example 89, emission having a peak wavelength of 550 nm was observed.

TABLE 18 Parameters for designed composition X M Element A Element D Element E Element Element Mn Ce Sm Eu Tb Dy Er Yb Ca Si Al N O Example a Value b Value c Value d Value e Value 85 0.0027 0.9973 1 1 3 0.0027 86 0.0027 0.9973 1 1 3 0.0054 87 0.0027 0.9973 1 1 3 0.0041 88 0.0027 0.9973 1 1 3 0.0041 89 0.0027 0.9973 1 1 3 0.0047 90 0.0027 0.9973 1 1 3 0.0041 91 0.0027 0.9973 1 1 3 0.0041 92 0.0027 0.9973 1 1 3 0.0041

TABLE 19 Mixing composition of raw powder (unit: % by weight) M Element A Element D Element E Element Example MnCO3 CeO2 Sm2O3 Eu2O3 Tb4O7 Dy2O3 Er2O3 Yb2O3 Ca3N2 Si3N4 AIN 85 0.22 35.95 34.01 29.82 86 0.33 35.91 33.97 29.78 87 0.34 35.91 33.97 29.78 88 0.341 35.91 33.97 29.78 89 0.36 35.9 33.96 29.77 90 0.36 35.9 33.97 29.78 91 0.37 35.9 33.96 29.77 92 0.38 35.89 33.96 29.77

TABLE 20 Peak wavelength and intensity of excitation and emission spectra on fluorescence measurement Excitation spectrum Emission spectrum Peak Strength Peak Intensity wavelength arbitrary wavelength arbitrary Example nm unit nm unit 85 449 1629 631 1703 86 466 2453 616 2592 87 310 3344 651 3344 88 449 6933 641 7032 89 255 2550 550 2550 90 248 7459 580 7509 91 449 1572 631 1630 92 448 821 640 833

Example 101

As raw powders were used an Eu₂O₃ powder, a Ca₃N₂ powder having an oxygen content of 9% by mol which is represented by mol number of oxygen relative to the total mol number of nitrogen and oxygen, an Si₃N₄ powder having an oxygen content as above of 2% by mol, and an AlN powder having an oxygen content as above of 2% by mol. Respective powders were weighed so as to be the metal element composition ratio (mol ratio) of Eu:Ca:Al:Si=0.008:0.992:1:1 and mixed to obtain a raw mixed powder. The oxygen content represented by mol number of oxygen relative to the total mol number of nitrogen and oxygen in the raw mixed powder was 5% by mol. In this connection, the Ca₃N₂ powder is a powder obtained by allowing oxygen to exist using raw materials to be baked containing only a desired concentration of oxygen, the Si₃N₄ powder is a powder obtained by allowing oxygen to exist using raw materials to be baked containing only a desired concentration of oxygen, the AlN powder is a powder obtained by allowing oxygen to exist using raw materials to be baked containing only a desired concentration of oxygen.

The raw mixed powder was placed in a crucible made of boron nitride without compression so as to be a bulk density of 0.35 g/cm³ and was baked at 1600° C. for 10 hours in a highly pure nitrogen atmosphere containing an oxygen concentration of 10 ppm or less at a nitrogen pressure of 1.1 atm using an electric furnace. At this time, the oxygen existing ratio in the raw material at baking is 5% by mol based on the calculation from the oxygen concentration in each raw material and the mixing ratio of each raw material.

As a result of identification of the crystal phase formed in the resulting phosphor by powder X-ray diffraction method, it was confirmed that CaAlSiN₃ family crystal phase was formed. When fluorescence properties of the phosphor were measured by excitation with a wavelength of 465 nm using a fluorescence spectrophotometer, the resulting phosphor showed a peak intensity of 128 in the case that the peak intensity of a commercially available yttrium aluminum garnet-based phosphor activated with Ce was regarded as 100, showing a high emission intensity, and a red light having a peak wavelength of 652 nm was observed. Moreover, 20 mg of the obtained phosphor sample was charged into a tin capsule, which was then placed in a nickel basket. Then, when the concentrations of oxygen and nitrogen in the powder sample were analyzed using a TC-436 Model oxygen and nitrogen analyzer manufactured by LECO, in the total of nitrogen and oxygen, it contained 94% by mol of nitrogen and 6% by mol of oxygen.

Example 102

A phosphor powder was obtained in the same manner as in Example 101 except that EuF₃ was used instead of Eu₂O₃. The oxygen content represented by mol number of oxygen relative to the total mol number of nitrogen and oxygen in the raw mixed powder was 5% by mol. Moreover, the oxygen existing ratio in the raw material at baking is 5% by mol based on the calculation from the oxygen concentration in each raw material and the mixing ratio of each raw material.

As a result of identification of the crystal phase formed in the resulting phosphor by powder X-ray diffraction method, it was confirmed that CaAlSiN₃ family crystal phase was formed. When fluorescence properties of the phosphor were measured by excitation with a wavelength of 465 nm using a fluorescence spectrophotometer, the resulting phosphor showed a peak intensity of 114 in the case that the peak intensity of a commercially available yttrium aluminum garnet-based phosphor activated with Ce was regarded as 100, showing a high emission intensity, and a red light having a peak wavelength of 650 nm was observed. Moreover, 20 mg of the obtained phosphor sample was charged into a tin capsule, which was then placed in a nickel basket. Then, when the concentrations of oxygen and nitrogen in the powder sample were analyzed using a TC-436 Mode: oxygen and nitrogen analyzer manufactured by LECO, in the total of nitrogen and oxygen, it contained 95% by mol of nitrogen and 5% by mol of oxygen.

Example 103

A phosphor powder was obtained in the same manner as in Example 101 except that EuN was used instead of Eu₂O₃ and the baking time was changed to 2 hours. The oxygen content represented by mol number of oxygen relative to the total mol number of nitrogen and oxygen in the raw mixed powder was 5% by mol. Moreover, the oxygen existing ratio in the raw material at baking is 5% by mol based on the calculation from the oxygen concentration in each raw material and the mixing ratio of each raw material.

As a result of identification of the crystal phase formed in the resulting phosphor by powder X-ray diffraction method, it was confirmed that CaAlSiN₃ family crystal phase was formed. When fluorescence properties of the phosphor were measured by excitation with a wavelength of 465 nm using a fluorescence spectrophotometer, the resulting phosphor showed a peak intensity of 112 in the case that the peak intensity of a commercially available yttrium aluminum garnet-based phosphor activated with Ce was regarded as 100, showing a high emission intensity, and a red light having a peak wavelength of 649 nm was observed. Moreover, 20 mg of the obtained phosphor sample was charged into a tin capsule, which was then placed in a nickel basket. Then, when the concentrations of oxygen and nitrogen in the powder sample were analyzed using a TC-436 Model oxygen and nitrogen analyzer manufactured by LECO, in the total of nitrogen and oxygen, it contained 95% by mol of nitrogen and 5% by mol of oxygen.

Example 104

A phosphor powder was obtained in the same manner as in Example 101 except that EuN was used instead of Eu₂O₃, the nitrogen pressure was changed to 10 atm, and the baking time was changed to 2 hours. The oxygen content represented by mol number of oxygen relative to the total mol number of nitrogen and oxygen in the raw mixed powder was 5% by mol. Moreover, the oxygen existing ratio in the raw material at baking is 5% by mol based on the calculation from the oxygen concentration in each raw material and the mixing ratio of each raw material.

As a result of identification of the crystal phase formed in the resulting phosphor by powder X-ray diffraction method, it was confirmed that CaAlSiN₃ family crystal phase was formed. When fluorescence properties of the phosphor were measured by excitation with a wavelength of 465 nm using a fluorescence spectrophotometer, the resulting phosphor showed a peak intensity of 109 in the case that the peak intensity of a commercially available yttrium aluminum garnet-based phosphor activated with Ce was regarded as 100, showing a high emission intensity, and a red light having a peak wavelength of 650 nm was observed. Moreover, 20 mg of the obtained phosphor sample was charged into a tin capsule, which was then placed in a nickel basket. Then, when the concentrations of oxygen and nitrogen in the powder sample were analyzed using a TC-436 Model oxygen and nitrogen analyzer manufactured by LECO, in the total of nitrogen and oxygen, it contained 95% by mol of nitrogen and 5% by mol of oxygen.

The results of Examples 101 to 104 are summarized in Table A.

TABLE A Fluorescence properties Baking conditions (465 nm excitation) Mixing ratio of Oxygen Peak raw materials Bulk existing ratio in Intensity Peak (molar ratio) density Temperature Time Pressure raw material Eu raw [relative wavelength Eu Ca Al Si [g/cm³] [° C.] [hour] [atm] [% by mol] material value] [nm] Example 0.008 0.992 1 1 0.35 1600 10 1.1 5 Eu₂O₃ 128 652 101 Example 0.008 0.992 1 1 0.35 1600 10 1.1 5 EuF₃ 114 650 102 Example 0.008 0.992 1 1 0.35 1600 2 1.1 5 EuN 112 649 103

The following will explain the lighting equipment using a phosphor comprising the nitride of the invention. FIG. 14 shows a schematic structural drawing of a white LED as a lighting equipment. Using a blue LED 2 of 450 nm as a light-emitting element, the phosphor of Example 1 of the invention and a yellow phosphor of Ca-α-sialon:Eu having a composition of Ca_(0.75)EU_(0.25)Si_(8.625)Al_(3.375)O_(1.125)N14.875 are dispersed in a resin layer to form a structure where the blue LED 2 is covered with the resulting resin layer. When electric current is passed through the electroconductive terminals, the LED 2 emits a light of 450 nm and the yellow phosphor and the red phosphor are excited with the light to emit yellow and red lights, whereby the light of LED and the yellow and red lights are mixed to function as a lighting equipment emitting a lamp-colored light.

A lighting equipment prepared by a combination design different from the above combination may be shown. First, using an ultraviolet LED of 380 nm as a light-emitting element, the phosphor of Example 1 of the invention, a blue phosphor (BaMgAl₁₀O₁₇:Eu), and a green phosphor (BaMgAl₁₀O₁₇:Eu,Mn) are dispersed in a resin layer to form a structure where the ultraviolet LED is covered with the resulting resin layer. When electric current is passed through the electroconductive terminals, the LED emits a light of 380 nm and the red phosphor, the green phosphor, and the blue phosphor are excited with the light to emit red, green, and blue lights, whereby these lights are mixed to function as a lighting equipment emitting a white light.

A lighting equipment prepared by a combination design different from the above combination may be shown. First, using a blue LED of 450 nm as a light-emitting element, the phosphor of Example 1 of the invention and a green phosphor (BaMgAl₁₀O₁₇:Eu,Mn) are dispersed in a resin layer to form a structure where the blue LED is covered with the resulting resin layer. When electric current is passed through the electroconductive terminals, the LED emits a light of 450 nm and the red phosphor and the green phosphor are excited with the light to emit red and green lights, whereby the blue light of LED and the green and red lights are mixed to function as a lighting equipment emitting a white light.

The following will explain a design example of an image display unit using the phosphor of the invention. FIG. 15 is a principle schematic drawing of a plasma display panel as an image display unit. The red phosphor of Example 1 of the invention, a green phosphor (Zn₂SiO₄:Mn), and a blue phosphor (BaMgAl₁₀O₁₇:Eu) are applied on the inner surface of cells 11, 12, and 13, respectively. When electric current is passed through electrodes 14, 15, 16, and 17, a vacuum ultraviolet ray is generated in the cells by Xe discharge and thereby the phosphors are excited to emit red, green, and blue visible lights. The lights are observed from the outside through the protective layer 20, the dielectric layer 19, and the glass substrate 22, whereby the unit functions as an image display.

While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof.

The present application is based on Japanese Patent Application No. 2003-394855 filed on Nov. 26, 2003, Japanese Patent Application No. 2004-41503 filed on Feb. 18, 2004, Japanese Patent Application No. 2004-154548 filed on May 25, 2004, and Japanese Patent Application No. 2004-159306 filed on May 28, 2004; and the contents are incorporated herein by reference.

INDUSTRIAL APPLICABILITY

The nitride phosphor of the invention exhibits emission at a longer wavelength as compared with conventional sialon and oxynitride phosphors and is excellent as a red phosphor. Furthermore, since luminance decrease of the phosphor is small when it is exposed to an excitation source, it is a nitride phosphor suitably used for VFD, FED, PDP, CRT, white LED, and the like. Hereafter, it is expected that the phosphor is widely utilized in material design in various display units and thus contributes development of industry. 

The invention claimed is:
 1. A phosphor comprising an inorganic compound represented by the composition formula: M_(a)A_(b)D_(c)E_(d)X_(e) wherein: M is one or two or more elements selected from the group consisting of Mn, Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, and Yb; A is one or two or more elements selected from the group consisting of divalent metal elements other than M Element; D is one or two or more elements selected from the group consisting of tetravalent metal elements; E is one or two or more elements selected from the group consisting of trivalent metal elements; X is one or two or more elements selected from the group consisting of O, N, and F; a+b=1; 0.00001≦a≦0.1; 0.5≦c≦1.8; 0.5≦d≦1.8; 0.8×(2/3+4/3×c+d)≦e; e≦1.2×(2/3+4/3×c+d).
 2. The phosphor of claim 1, wherein the inorganic compound has the same crystal structure as CaAlSiN₃ or a crystal structure such that: positions of skeletal atoms in the inorganic compound are not sufficiently different from skeletal atoms in CaAlSiN₃ that corresponding chemical bonds are cleaved; and lengths of chemical bonds in the inorganic compound corresponding to Al—N and Si—N bonds in CaAlSiN₃ differ from lengths of Al—N and Si—N bonds in CaAlSiN₃ by +15%.
 3. The phosphor of claim 1, wherein the inorganic compound comprises CaAlSiN₃:Eu.
 4. The phosphor according to claim 1, wherein: A is one or two or more elements selected from the group consisting of Mg, Ca, Sr, and Ba; D is one or two or more elements selected from the group consisting of Si, Ge, Sn, Ti, Zr, and Hf; and E is one or two or more elements selected from the group consisting of B, Al, Ga, In, Sc, Y, La, Gd, and Lu.
 5. The phosphor according to claim 1, wherein: M comprises Eu; A comprises Ca; D comprises Si; E comprises Al; and X comprises N.
 6. The phosphor according to claim 1, wherein the inorganic compound is a CaAlSiN₃ crystal phase or a solid solution of a CaAlSiN₃ crystal phase.
 7. The phosphor according to claim 1, wherein: M comprises Eu; A comprises Ca; D comprises Si; E comprises Al; and X comprises a mixture of N and O.
 8. The phosphor according to claim 1, wherein A comprises Sr.
 9. The phosphor according to claim 8, wherein numbers of atoms of Ca and Sr in the inorganic compound satisfy: 0.02≦(number of atoms of Ca)/{(number of atoms of Ca)+(number of atoms of Sr)}<1.
 10. The phosphor according to claim 1, wherein X comprises N and O.
 11. The phosphor according to claim 10, wherein numbers of atoms of O and N in the inorganic compound satisfy: 0.5≦(number of atoms of N)/{(number of atoms of N)+(number of atoms of 0)}≦1.
 12. The phosphor according to claim 10, wherein the inorganic compound is represented by: M_(a)A_(b)D_(1−x)E_(1+x)N_(3−x)O_(x) wherein: a+b=1; and 0<x≦0.5.
 13. The phosphor according to claim 1, wherein: the inorganic compound is in the form of a powder; the powder has an average particle size of 0.1 μm to 20 μm; and the powder comprises single crystal particles or aggregates of single crystals.
 14. The phosphor according to claim 1, wherein the inorganic compound comprises impurity elements of Fe, Co, and Ni in an amount of 50 ppm or less.
 15. The phosphor according to claim 1, comprising the inorganic compound and a further crystal phase or amorphous phase; wherein the inorganic compound is present in an amount of at least 20% by weight based on a total weight of the inorganic compound and the further crystal phase or amorphous phase.
 16. The phosphor according to claim 15, wherein the further crystal phase or amorphous phase comprises an inorganic substance having electroconductivity.
 17. The phosphor according to claim 16, wherein the inorganic substance having electroconductivity is a material comprising an oxide, oxynitride, or nitride comprising one or two or more elements selected from the group consisting of Zn, Al, Ga, In, and Sn.
 18. The phosphor according to claim 15, wherein the further crystal phase or amorphous phase differs in composition from the inorganic compound.
 19. The phosphor according to claim 1, wherein the phosphor emits a fluorescent light having a peak wavelength of from 570 nm to 700 nm, when irradiated with an excitation source.
 20. The phosphor according to claim 19, wherein the excitation source is an ultraviolet ray or visible light having a wavelength of 100 nm to 600 nm.
 21. The phosphor according to claim 19, wherein: the inorganic compound is a CaAlSiN₃ crystal phase; Eu is dissolved in the crystal phase; and the phosphor emits a fluorescent light having a peak wavelength of from 600 nm to 700 nm, when irradiated with light having a wavelength of from 100 nm to 600 nm.
 22. The phosphor according to claim 19, wherein the excitation source is an electron beam or an X-ray.
 23. The phosphor according to claim 19, wherein the phosphor emits fluorescent light having a color satisfying: 0.45≦x≦0.7 as a value of (x, y) on the CIE coordinates. 